Kotoho Sakuragawa

 (桜川 寿, Sakuragawa Kotoho ) is a woman who works in forensics in the Shinjuku Police Department. She is following the X-Day cases independently. When Hoshino investigates the X-Day cases, Sakuragawa aids her various ways such as showing her case materials. Although she is cold upon first meeting, she eventually becomes good friends with Hoshino.