1. The plaintiff's appeal is dismissed.

2. The costs of appeal shall be borne by the Plaintiff.

The purport of the claim and appeal is the purport of the appeal.

Basic Facts

The reasoning for this part of this Court's explanation is that it is identical to the corresponding part of the reasoning of the judgment of the first instance.

(Article 420 of the Civil Procedure Act). For the following reasons, the Defendant is obligated to pay to the Plaintiff the down payment of KRW 77.9 million and penalty of KRW 2,337,00,000 paid by the Plaintiff, as well as damages for delay.

Since there is a system for inspecting the flow water that needs to be continuously checked by a third party, it is almost impossible to use and benefit from the commercial area in the front of the inquiry to enter the place with a system for inspecting the flow water. Therefore, it is the defect of the contract object.

Since the plaintiff cannot achieve the purpose of the sales contract of this case due to these defects, the contract of this case is cancelled based on the warranty liability under the Civil Act.

In addition, the defendant is obligated to notify the above entrance of the fact that it is inside the commercial building of this case in accordance with the principle of good faith, and as such, the contract of this case is cancelled for this reason.

Under the sales contract of this case, the exclusive use area of the commercial building of this case constitutes an important part of the legal act. The plaintiff's mistake in the establishment of the above entrance and the possibility of actual use and profit-making therefrom is an important part of the legal act.

(I) The sales contract of this case is revoked on the ground of mistake.

Judgment

The fact that there is a door from the inside of the commercial building of this case to allow access to the place where the water-flow source inspection device is installed, as seen earlier, is based on the aforementioned facts.

However, in light of the above facts, evidence, and the overall purport of the pleading, it is impossible to use the above recognized facts and the evidence submitted by the Plaintiff alone in the front space of the wall where the entrance is installed.

(b).