Jin-woo who is in 3rd grade in elementary school takes care of the house as his father asked. However, his younger brother Sun-woo was in a playground playing with his dog, meets a 6th grader Chan-young. Chanyoung, who is a bully, steals Sunwoo's dog. When Sunwoo comes back home crying, Jin-woo conflicts between keeping the promise with his father and standing up to Chanyoung to take their dog back.

Jin-woo who is in 3rd grade in elementary school takes care of the house as his father asked. However, his younger brother Sun-woo was in a playground playing with his dog, meets a 6th grader Chan-young. Chanyoung, who is a bully, steals Sunwoo's dog. When Sunwoo comes back home crying, Jin-woo conflicts between keeping the promise with his father and standing up to Chanyoung to take their dog back.