The plaintiff is a merchant who is engaged in the construction and artificial fishery in the trade name of Jongno-gu Seoul Metropolitan Government, and the defendant is a person who owns the second floor house located in Jongno-gu Seoul Metropolitan Government D (hereinafter referred to as the "instant house").

On December 12, 2015, the Plaintiff: (a) remodeled the instant house from the Defendant to rebuild the walls and floors; (b) removed the walls and floors; (c) newly built a dunes; (d) newly built a dunes; (e) entrusted a large remodeling project, such as high-class finishing materials and high-class interior materials, and performing artificial engineering works; and (e) performed a large remodeling project on December 12, 2015 without preparing a fixed term contract; and (e) commenced the construction immediately after having received KRW 40,000 from the Defendant on December 12, 2015.

(hereinafter “this case’s construction work”). The Plaintiff offered a written estimate (No. 5(1) through (14) to the Defendant, at the Defendant’s request, the construction specifications and the cost accounting statement are written in detail.

The defendant requested to change part of the construction work contents over several occasions and the plaintiff provided a written estimate to meet the defendant's demand.

The Plaintiff and the Defendant carried out construction works without accurate agreement of construction cost. On December 12, 2016, the Defendant paid 40,000,000 won for the first installment payment, 20,000,000 won for the second installment payment on December 30, 2016, and 80,000,000 won for the last installment payment on January 16, 2017, the construction contract was completely concluded on February 28, 2017, while the construction was temporarily suspended on February 28, 2017.

According to the contract (Evidence A) concluded on February 28, 2017, the total construction cost of the instant construction is KRW 190,000,000 (excluding value-added tax) and the construction period is up to April 10, 2017. The Defendant shall pay KRW 30,000 of intermediate payment, KRW 40,000,000, and KRW 21,000,000 of intermediate payment, March 15, 2017, and KRW 21,00,00,000, respectively, within one week after the completion of the construction work.