The defendant's KRW 53,887,891 to the plaintiff and its related 6% per annum from March 20, 2019 to January 20, 2021, and the following.

1. Basic facts

A. The plaintiff is a corporation established for the purpose of construction business, etc., and the defendant is a personal entrepreneur who runs construction business under the trade name C.

B. On January 30, 2017, the Defendant was awarded a contract with D Co., Ltd. (hereinafter “D”) to KRW 387,071,00 (including value added tax) for the new construction of Gangnam-gu Seoul E apartment complex.

The Defendant entered into a subcontract with the Plaintiff on the instant construction works inside and outside of the Republic of Korea (hereinafter “instant construction works”), and the Plaintiff completed the instant construction works in accordance with the said subcontract.

(c)

The Plaintiff received KRW 103,328,828 in total, and KRW 49,500,000 from D, respectively, from April 10, 2017 to May 13, 2017.

[Grounds for Recognition] Unsatisfy, Gap evidence Nos. 8 through 11, Eul evidence No. 1, the purport of the whole pleadings

2. Determination on the cause of the claim

A. On March 7, 2017, the Plaintiff agreed with the Defendant to pay the instant construction cost of KRW 185,460,000 (= value added KRW 168,60,000) (= value added KRW 16,860,00).

However, according to the agreement with the Defendant, the Plaintiff decided to increase the construction cost of this case to KRW 297,220,000 (i.e., value added tax of KRW 270,200,000) according to the quotation on April 28, 2017.

Therefore, the Defendant is obligated to pay 144,391,172 won (=29,220,00 won - 152,828,828 won), excluding 152,828 won (i.e., 103,328,828 won paid by the Defendant from D) paid by the Plaintiff to the Plaintiff (i.e., KRW 297,220,00) and damages for delay.

B) Even if there was no agreement between the Plaintiff and the Defendant on additional construction

Even if the defendant obtained a benefit equivalent to KRW 144,391,172 as above due to the plaintiff's additional construction work, and thus, he is obligated to return it to the plaintiff with unjust benefit. Thus, the defendant is liable to compensate the plaintiff for damages incurred and delayed payment.