Young MON, whose real name is unknown

Kaede, a high school student with nothing to do during the summer vacation, stumbles upon Hatano, a classmate from the same school, burglarizing a shabby apartment next to a red bridge near his home, only to discover that there is a child living alone hidden in the apartment! He was only holding a rag doll, with big watery eyes. He didn't speak or make any noise. He lived in this dilapidated house for some reason. Hatano named him "MON". Two high school girls acted as baby mothers and began to secretly take care of him without telling everyone. One day, they met the staff of the small town's Children's Counseling Office and were told that MON might have been abused as a child and given up by his biological mother...