When the parties have reciprocally declared their concordant intent, either expressly or impliedly, a contract shall be constituted.
If the parties agree on all the essential elements of the contract but have expressed no intent as to the non-essential elements, the contract shall be presumed to be constituted. In the absence of an agreement on the above-mentioned non-essential elements, the court shall decide them according to the nature of the affair.

A person who offers to make a contract shall be bound by his offer except at the time of offer he has excluded this obligation or except it may be presumed from the circumstances or from the nature of the affair that he did not intend to be bound.
Exposing goods for sale with their selling price shall be deemed to be an offer. However, the sending of pricelists is not deemed to be an offer.

An offer ceases to be binding if it is refused.

An offer made inter presentes ceases to be binding if it is not accepted at once.

An offer made inter absentes ceases to be binding if it is not accepted by the other party within the time during which notice of acceptance may be expected to arrive under ordinary circumstances.

If a period of time for the acceptance of the offer has been fixed, the offer ceases to be binding if it is not accepted within such period.

If an acceptance arrives late though it should usually arrive within a reasonable time by its transmitting manner, and this might be known to the offerer, the offerer should immediately notify the acceptor of such delay.
If the offerer delays the notice specified in the preceding paragraph, the acceptance shall be deemed to have arrived without delay.

An acceptance which arrives late, except under the circumstances in the preceding article, shall be deemed to be a new offer.
An acceptance with amplifications, limitations or other alterations shall be deemed to be a refusal of the original offer and the making of a new offer.

In cases where according to customs or owing to the nature of the affair, a notice of acceptance is not necessary, the contract shall be constituted when, within a reasonable time, there is a fact, which may be considered as an acceptance of the offer.
The provision of the preceding paragraph shall be mutatis mutandis applied when at the time of offer the offerer has waived notice of acceptance.

If a notice of withdrawing an offer arrives after the arrival of the offer itself, though it should usually arrive before or simultaneously with the arrival of the offer within a reasonable time by its transmitting manner, and this might be known to the other party, the other party so notified should notify the offerer immediately of such delay.
If such other party delays the notice specified in the preceding paragraph, the notice of withdrawing the offer shall be deemed to have arrived without delay.

The provisions of the preceding article shall apply mutatis mutandis to the withdrawal of acceptance.

When a public notice promises to reward the person for his performance of a particular act, it is a rewarding public notice. The promisor is bound to deliver the reward to the person who has performed the act.
When the act specified in the preceding paragraph has been successively performed by several persons, it is the person who has performed first acquires the claim for reward; when the act has been performed jointly by several persons or performed simultaneously by several persons respectively, it is these persons who acquire the claim for reward jointly.
In the preceding paragraph, if the promisor has delivered the reward in good faith to the person who has first notified his performance, the obligation of the promisor to deliver the reward shall be extinguished.
The provisions of the preceding three paragraphs shall apply mutatis mutandis to the person who has performed such act specified in the public notice without knowing of this notice.

If there is a specific right acquired because of the performance of an act in the preceding article, this right shall belong to the person who has performed the act, unless otherwise notified in the public notice.

When a promise of reward made by a public notice is withdrawn before the act is performed, the promisor is bound to compensate the person performing the act in good faith for the injury arising therefrom, unless the promisor can prove that the person could have never performed the act. The compensation shall not exceed the amount of the promised reward.
When there is a period of time fixed for the performance in the public notice, the promisor is presumed to waive his withdrawing right.

If a public notice promises to reward the person who has performed a particular act, notified within a certain period of time and has been evaluated as the best, it is a rewarding public notice for the best. The promisor is bound to deliver the reward in the completion of the evaluation.

The evaluation in the preceding article shall be proceeded by the person appointed in the public notice. If there is no any appointment in the public notice, it shall be proceed with the manner decided by the promisor.
The evaluation according to the provision of the preceding paragraph shall be binding on the promisor and the promisee.

If there are several persons evaluated as the best, unless otherwise notified in the public notice, these persons acquire the claim for reward jointly.

The provision of Article 164-1 shall apply mutatis mutandis to the rewarding public notice for the best.

If it is agreed between the parties that a contract shall be made in a certain definite form, the contract is presumed to be not constituted before the completion of such form.

If a contract is made for the obligations of the transferring, creation, or altering of rights over the real property, it shall be made in the notarization made by the notary public.
A contract not notarized according to the provision of the preceding paragraph could still be valid if the parties have agreed on the transferring, creation, or altering of rights over the real property and have completed the recordation.

If authority of agency is conferred by a juridical act, it shall be made by an expression of intent to the agent or to the third party with whom the delegated act is transacted.

If there are several agents, the delegated act shall be transacted by them jointly, unless otherwise provided by the act or the principal's expression of intent.

A person, who by his own acts represents he has conferred the authority of agency to another person, or who knows that another person declares himself to be his agent and failed to express a contrary intent, shall be liable to the third party as a person who has conferred that authority, except the third party knew, or might know of the absence of authority.

A juridical act made in the name of an agent by a person of no authority of agency shall not be effective to the principal except it is acknowledged by the principal.
In the case specified in the preceding paragraph, the other party to the juridical act may fix a reasonable period and request the principal to declare definitely whether he acknowledges it or not. If the principal does not give a definite answer within the specified period, the acknowledgement shall be deemed to have been refused.

[The expression of intend in]A juridical act made by a person of no authority of agency may be withdrawn by the other party to the act before the acknowledgement of the principal, except where such other party knew of the absence of authority at the time of the act.

A person, who manages an affair of another person without a mandate or obligation, shall manage the affair in conformity with the principal's expressed or presumptive wishes and in the manner beneficial to the principal.

The manager shall notify the principal without delay at the beginning of the management in so far as the notice is possible. If there is no urgency, he shall wait for the instructions of the principal.
The provisions of Articles 540 to Article 542 concerning Mandate shall apply mutatis mutandis to Management of Affairs without Mandate.

If the undertaking of the management of the affair is against the principal's expressed or presumptive wishes, the manager is bound to compensate the principal for any injury arising from his management, even if no negligence is in his act.
The provision of the preceding paragraph shall not apply if the undertaking of the management of the affair is in order to fulfill an obligation of public interests for the principal or to fulfill a statutory duty of the principal to furnish maintenance to others, or the principal's wishes are against the public policy or morals.

If the undertaking of the management of the affair is in order to avert an imminent danger which threatens the life, body or property of the principal, the manager is not responsible for any injury derived from his management, except in case of bad faith or gross negligence.

If the management of the affair is beneficial to the principal and is not against his expressed or presumptive wishes, and where the manager has, for the principal, made necessary or beneficial expenses, or assumed debt, or suffered injury, he is entitled to claim against the principal for the reimbursement of such expenses plus interest commencing from the date of outlay, or the payment of such debt, or compensation for the injury sustained.
In the cases provided by the second paragraph of Article 174, the manager may still have the claim in the preceding paragraph, even if the undertaking of the management of the affair is against the principal's wishes.

If the management of the affair does not accord with the provisions of the preceding article, the principal may still be entitled to the interests derived from the management. But the obligation specified in the first paragraph of the preceding article of the principal towards the manager shall be only to the extent of the interests he acquired.
The provision of the preceding paragraph shall apply mutatis mutandis to the situation when the manager knew it was another person's affair but still managed for his own interests.

If the management of the affair is acknowledged by the principal, unless otherwise expressed by the parties, from the beginning of the management, the provisions concerning Mandate shall be applied.

A person who acquires interests without any legal ground and prejudice to the other shall be bound to return it. The same rule shall be applied if a legal ground existed originally but disappeared subsequently.

In any of the following cases, the prestation shall not be claimed to return:
(1) If the prestation was for the performance of a moral obligation;
(2) If the prestation made by the debtor for the performance of an undue obligation;
(3) If the person who has made a prestation for the purpose of performing an obligation knew, at the time of performance, that he was not bound to perform;
(4) If the prestation was made for an unlawful cause. Except when the unlawful cause exists only with regard to the recipient.

In addition to the interests received, a recipient unjustly enriched shall return whatever he acquired by virtue of such interests. If restitution is impossible by reason of the very nature of the interests or by reason of any other circumstance, he shall be bound to reimburse the value.

The recipient, who did not know of the absence of the legal ground and the interests have no longer existed, is released from the obligation to return the interests or reimburse the value.
If the recipient knew of the absence of the legal ground at the time of the receipt, or if he was subsequently aware of it, he shall be bound to return the interests acquired at the time of the receipt or such interests still existing at the time when he was aware of the absence of the legal ground plus the interest and to make compensation for the injury, if any.

When the recipient unjustly enriched transferred gratuitously whatever he has received to a third party, and therefore the recipient is released from his obligation to return the interests, such third party shall be bound to make restitution to the extent which the recipient is released from his obligation.

A person who, intentionally or negligently, has wrongfully damaged the rights of another is bound to compensate him for any injury arising therefrom. The same rule shall be applied when the injury is done intentionally in a manner against the rules of morals.
A person, who violates a statutory provision enacted for the protection of others and therefore prejudice to others, is bound to compensate for the injury, except no negligence in his act can be proved.

If several persons have wrongfully damaged the rights of another jointly, they are jointly liable for the injury arising therefrom. The same rule shall be applied even if which one has actually caused the injury cannot be sure.
Instigators and accomplices are deemed to be joint tortfeasors.

An official, who has intentionally committed a breach of duty which he ought to exercise in favor of a third party and therefore prejudice to such third party, is liable for any injury arising therefrom. If the breach is the result of this official's negligence, he may be held liable to compensate only in so far as the injured person is unable to obtain compensation by other means.
In the case mentioned in the preceding paragraph, if the injured person who may obviate the injury by making use of a legal remedy has intentionally or negligently omitted to make use of it, the official shall not be liable to compensate for the injury.

A person of no capacity or limited in capacity to make juridical acts, who has wrongfully damaged the rights of another, shall be jointly liable with his guardian for any injury arising therefrom if he is capable of discernment at the time of committing such an act. If he is incapable of discernment at the time of committing the act, his guardian alone shall be liable for such injury.
In the case of the preceding paragraph, the guardian is not liable if there is no negligence in his duty of supervision, or if the injury would have been occasioned notwithstanding the exercise of reasonable supervision.
If compensation cannot be obtained according to the provisions of the preceding two paragraphs, the court may, on the application of the injured person, take the financial conditions among the tortfeasors, the guardian and the injured person into consideration, and order the tortfeasors or his guardian to compensate for a part or the whole of the injury.
The provision of the preceding paragraph shall apply mutatis mutandis to cases where the injury has been caused to a third party by a person other than those specified in the first paragraph in a condition of unconsciousness or of mental disorder.

The employer shall be jointly liable to make compensation for any injury which the employee has wrongfully caused to the rights of another in the performance of his duties. However, the employer is not liable for the injury if he has exercised reasonable care in the selection of the employee, and in the supervision of the performance of his duties, or if the injury would have been occasioned notwithstanding the exercise of such reasonable care.
If compensation cannot be obtained according to the provision of the preceding paragraph, the court may, on the application of the injured person, take the financial conditions of the employer and the injured person into consideration, and order the employer to compensate for a part or the whole of the injury.
The employer who has made compensation as specified in the preceding paragraph may claim for reimbursement against the employee committed the wrongful act.

The proprietor is not liable for the injury wrongfully caused by an undertaker to the rights of another in the course of his work, unless the proprietor was negligent in regard to the work ordered or his instructions.

If injury is caused by an animal, the possessor is bound to compensate the injured person for any injury arising therefrom, unless reasonable care in keeping according to the species and nature of the animal has been exercised, or unless the injury would have been occasioned notwithstanding the exercise of such reasonable care.
The possessor may claim for reimbursement against the third party, who has excited or provoked the animal, or against the possessor of another animal which has caused the excitement or provocation.

The injury, which is caused by a building or other work on privately owned land, shall be compensated by the owner of such building or work, unless there is no defective construction or insufficient maintenance in such building or work, or the injury was not caused by the defectiveness or insufficiency, or the owner has exercised reasonable care to prevent such injury.
In the case of the preceding paragraph, if there is another person who shall be responsible for the injury, the owner making compensation may make a claim for reimbursement against such person.

The manufacturer is liable for the injury to another arising from the common use or consumption of his merchandise, unless there is no defectiveness in the production, manufacture, process, or design of the merchandise, or the injury is not caused by the defectiveness, or the manufacturer has exercised reasonable care to prevent the injury.
The manufacturer mentioned in the preceding paragraph is the person who produces, manufactures, or processes the merchandise. Those, who attach the merchandise with the service mark, or other characters, signs to the extent enough to show it was produced, manufactured, or processed by them, shall be deemed to be the manufacturer.
If the production, manufacture, process, or design of the merchandise is inconsistent with the contents of its manual or advertisement, it is deemed to be defective.
The importer shall be as liable for the injury as the manufacturer.

If an automobile, motorcycle or other motor vehicles which need not to be driven on tracks in use has caused the injury to another, the driver shall be liable for the injury arising therefrom, unless he has exercised reasonable care to prevent the injury.

The person, who runs a particular business or does other work or activity, shall be liable for the injury to another if the nature of the work or activity, or the implement or manner used might damage to another. Except the injury was not caused by the work or activity, or by the implement or manner used, or he has exercised reasonable care to prevent the injury.

A person who has wrongfully caused the death of another shall also be bound to make compensation for the injury to any person incurring the medical expenses, increasing the need in living, or incurring the funeral expenses.
If the deceased was statutorily bound to furnish maintenance to a third party, the tortfeasor shall also make compensation to such third party for any injury arising therefrom.
The provision of the second paragraph of Article 193 shall apply to the compensation of the preceding paragraph.

If a person has wrongfully damaged to the body or health of another, and caused the injured person to lose or decrease his laboring capacity, or to increase the need in living, the tortfeasors shall be bound to make compensation to the injured person for any injury arising therefrom.
The court may, on the application of the parties, order the compensation of the preceding paragraph to be made in periodical payments of money, but the court shall compel the tortfeasor to furnish security.

In case of death caused by a wrongful act, the father, mother, sons, daughters and spouse of the deceased may claim for a reasonable compensation in money even if such injury is not a purely pecuniary loss.

If a person has wrongfully damaged to the body, health, reputation, liberty, credit, privacy or chastity of another, or to another's personality in a severe way, the injured person may claim a reasonable compensation in money even if such injury is not a purely pecuniary loss. If it was reputation that has been damaged, the injured person may also claim the taking of proper measures for the rehabilitation of his reputation.
The claim of the preceding paragraph shall not be transferred or inherited, except a claim for compensation in money has been promised by contract or has been commenced.
The provisions of the preceding two paragraphs shall be mutatis mutandis applied when a person has wrongfully damaged to another's status based on the relationship to their father, mother, sons, daughters, or spouse in a severe way.

If a person has wrongfully damaged to a thing which belongs to another, the injured person may claim to make compensation for the diminution of the value of the thing.

The claim for the injury arising from a wrongful act shall be extinguished by prescription, if not exercised within two years from the date when the injury and the person bound to make compensation became known to the injured person. The same rule shall be applied if ten years have elapsed from the date when the wrongful act was committed.
A person bound to make compensation shall, even after the completion of prescription under the preceding paragraph, return to the injured person in accordance with the provisions concerning Unjust Enrichment whatever he has acquired through a wrongful act and therefore prejudiced to the injured person.

If a person acquires a claim against the injured person by a wrongful act, the latter may still refuse to perform even if the claim for avoidance has been extinguished by prescription.