北舘 充

Mitsuru is Keisuke's younger brother, he considers him as if he were his real father. A few years earlier, Mitsuru was in big trouble and his older brother decided to look after him. During all his years in college, Keisuke kept supporting him, telling him that he was and was doing his pride and when Mitsuru found a job, his older brother was overjoyed. However, his brother then told him that he had established a relationship with a certain Yura and that he had decided to propose to her.

Mitsuru was very happy for his brother, even though he knew that this news also announced the beginning of a life of loneliness for him. Unfortunately, a few months later after Mashiro's birth, Keisuke had a car accident and died in the ambulance that took him to the hospital. Very sad for his brother and his nascent family, Mitsuru decided not to let fate dictate their lives and decided to give back to his sister-in-law and niece what his brother had given him before, a family.