1. The plaintiff's appeal and the defendant's incidental appeal are all dismissed.

2. The costs of appeal are assessed against the Plaintiff.

1. Basic facts

A. The Plaintiff is a mutual aid business operator who has entered into a motor vehicle mutual aid contract with respect to A vehicles (hereinafter “Plaintiffs”). The Defendant is an insurer who entered into a comprehensive motor vehicle mutual aid contract with respect to B vehicles (hereinafter “Defendant vehicles”).

B. On June 8, 2017, around 5:10, the Plaintiff’s vehicle changed rapidly from three lanes to one lane on the front side of the Defendant’s vehicle located in Seo-gu, Seo-gu, Gwangju (hereinafter “instant traffic accident”) in order for the Plaintiff’s vehicle to walk in the opposite road beyond the center line and go beyond the center line as indicated in the attached Form No. D’s site map, which led to a sudden change of the lanes from three lanes to one lane. As the part behind the Plaintiff’s vehicle, the front part of the Defendant’s vehicle driven in accordance with the same direction as the part following the vehicle (hereinafter “instant traffic accident”).

C. The instant traffic accident destroyed the F filling Station wall, wall, etc. located on the road dump, while the gas tank attached inside the Plaintiff’s vehicle is far away.

On August 1, 2017, the Plaintiff paid KRW 1,800,000, as a mutual aid business entity of Plaintiff vehicle, to Taepyeong Construction Co., Ltd., for damages incurred from the damage of the said fences, walls, etc.

[Ground of recognition] Facts without dispute, Gap evidence Nos. 1 through 3, Eul evidence No. 3 (including branch numbers, hereinafter the same), Gap evidence No. 10, and the purport of whole pleadings

2. The parties' assertion

A. The Plaintiff’s principal cause of the instant traffic accident is bound by the Defendant’s vehicle’s main cause, and thus, the ratio of Defendant’s vehicle’s liability is 50%, and the Plaintiff paid KRW 1,800,000 to Taesung Construction Co., Ltd. for damages incurred from the instant traffic accident according to the mutual aid agreement. As such, the Defendant is obligated to pay the Plaintiff the indemnity amount of KRW 900,000 (= KRW 1,800,000 x 50%) and damages for delay.

B. The instant traffic accident alleged by the Defendant was occurred in the course of the illegal internship of the Plaintiff’s vehicle, and the Defendant.