1. The plaintiff (Counterclaim defendant)'s appeal against the principal lawsuit is dismissed.

2. The part concerning the counterclaim among the judgment of the court of first instance is relevant.

1. The reasoning of the judgment of the court of first instance cited this case is that the relevant part of the judgment of the court of first instance is identical to the relevant part of the judgment of the court of first instance, except for alteration or addition as set forth in paragraph (2) below.

2.At the end of the nine pages of any modification or addition, the following shall be added at the end of four:

In regard to this, the Plaintiff asserted that the contract becomes effective even if the Defendant cancels the contract of this case on the ground of the Plaintiff’s nonperformance, since the development under the contract of this case was considerably advanced, and thus, the contract becomes more beneficial to the Defendant. In addition, in a case where the construction is considerably advanced even if there is an incomplete portion in the construction contract, and the restoration to its original state would incur serious social and economic losses, and the completed portion would benefit to the contractor, when the contractor cancels the contract on the ground of the contractor’s nonperformance, the contract should only be deemed effective when the contractor cancels the contract (see Supreme Court Decision 85Meu1751, Sept. 9, 1986). However, in this case, the Plaintiff’s construction of a system related to software development, etc., and the aforementioned Supreme Court’s decision regarding the construction of construction contract of this case is different from the Plaintiff’s construction of a system under Article 4, 7, 12 and 13% of the construction contract, the Plaintiff’s submission of the evidence and evidence in the first instance court’s order as well as evidence.