2. The plaintiff's claim is dismissed.

3. All costs of the lawsuit shall be borne by the Plaintiff.

A. On November 2, 2017, the Plaintiff requested Nonparty E, who was the owner of C (fishing vessel number: D. 9.7 tons; hereinafter “instant fishing vessel”) to install a professional propeller, showers, and propellers, etc. (hereinafter “voluntary propeller, etc.”) in the instant fishing vessel (hereinafter “instant contract for installation of propellers, etc.”). At that time, Nonparty E completed the installation of propellers, etc., but Nonparty E did not pay 15 million won for the installation of propellers, etc. to the Plaintiff.

B. Nonparty F, the inheritor upon the death of Nonparty E, transferred all the rights to the construction of the instant fishing vessel to the Defendant (hereinafter “instant comprehensive acquisition agreement”), and thereafter, the Defendant built the said fishing vessel in G fishing boat and acquired its ownership on January 31, 2018.

C. Therefore, according to the instant comprehensive acquisition agreement, the Defendant is obligated to pay the Plaintiff the installation cost of KRW 15 million and its delay damages in accordance with the agreement.

2. Determination

A. The evidence presented by the Plaintiff alone is insufficient to acknowledge that the comprehensive acquisition of the instant fishing vessel between Nonparty F and the Defendant, the inheritor of Nonparty E, was a contract. There is no other evidence to acknowledge this. Therefore, the Plaintiff’s assertion premised on this premise is without merit without examining the remainder of the issue.

B. The plaintiff asserts that "the defendant did not pay 15 million won for the installation of propellers, etc. to G Shipbuilding, which is the shipbuilding owner of the fishing vessel of this case (the manufacturing price at a low price equivalent to the above installation price) and acquired the ownership of the fishing vessel from the above shipbuilding station." Even if the plaintiff's assertion was made by unjust enrichment return, the fact that the contract between the plaintiff and the non-party E entered into between the plaintiff and the plaintiff for the installation of propellers, etc. is without dispute between the parties. The plaintiff is not the non-party E or his heir, who is the party to the contract, but rather the interest of the construction of the fishing vessel of this case.