A. The plaintiff is a stock company established for the purpose of construction business, etc., and the defendant is a reconstruction association established on June 21, 2002 pursuant to the Act on the Maintenance and Improvement of Urban Areas and Dwelling Conditions for Residents in order to implement a housing reconstruction improvement project (hereinafter "the reconstruction project of this case") on the land of five lots, such as Bupyeong-gu Incheon Metropolitan City F (hereinafter "the land of this case"). The defendant is a member of the defendant association.

B. On February 8, 2002, the Defendant entered into a joint agreement on the instant reconstruction project with a lender Construction Co., Ltd. (hereinafter referred to as the “Large Construction”), and around 2006, entered into a modified agreement on partial revision of the said joint agreement (hereinafter referred to as the “instant joint agreement”).

The main content of the instant joint project agreement is that the lender and the joint project owner shall perform the removal of existing structures on the land of this case, the construction of new apartments, and the sale of general apartment units in lots, as the contractor and the joint project owner.

C. On the instant land, there was a power transmission line connected to one of the power transmission towers established by the Korea Electric Power Corporation and one of the said transmission towers (hereinafter “the instant power transmission tower, etc.”). However, the lender, for the instant reconstruction project, performed the removal and removal of the instant transmission tower, etc. for the purpose of the instant reconstruction project. Meanwhile, according to the instant joint project agreement, the lender is to bear the costs of the said removal and removal within the scope of KRW 3,493,182,650 for the said removal and removal.

On December 6, 2007, the Defendant terminated the instant joint project agreement with the lender. Around March 27, 2008, the lender was demanding the Defendant to return KRW 3,936,917,245, such as loans, operating expenses, etc. paid by the lender under the instant joint project agreement, and the said amount was included in the removal of transmission towers, etc. and the use of facilities.