1. The plaintiff's appeal and the conjunctive claim added by this court are all dismissed.

2. After an appeal is filed.

1. The reasoning of the judgment of the court of first instance that cited the reasoning of the judgment is as follows, and the reasoning of the judgment of the court of first instance is the same as the reasoning of the judgment of the court of first instance, except for the case where the plaintiff additionally determines the claim added in this court as the conjunctive claim, and thus, it is acceptable in accordance with the main sentence of Article 420 of the Civil Procedure Act.

In order to cancel a juristic act on the ground that the mistake in the motive for determination as to whether a juristic act constitutes an expression of intent by mistake falls under the mistake in the important part of the contents of the juristic act, it is sufficient to indicate the motive to be the content of the said expression of intent to the other party and it is recognized that it constitutes the content of the juristic act in the interpretation of the expression of intent, and it is not necessary to reach an agreement to separately consider the motive as the content of the juristic act between the parties (see, e.g., Supreme Court Decision 95Da516, Nov. 21, 1995). However, the error in the contents of the juristic act must be related to the important part to such extent that it would have been deemed that if the ordinary general public would not express his/her intent if it entered into the position of the person who made the expression of intent (see, e.g., Supreme Court Decision 93Da55487, Mar. 26, 1996).

In full view of the written statements and images of Gap evidence Nos. 3 through 5 and 8, the building of this case was modified to a residential purpose, such as removing balconys and building rooms, from the structure originally approved for use. On the premise of this, the plaintiff entered into a lease contract with the defendant. The plaintiff was on the part of the defendant at the time of termination of the lease contract.