八木沼 了一

A police officer who was part of the investigation team for the Ueno's serial killer and murder mystery. After the case was solved, he was transferred and promoted and became a police officer of the National Police Agency in the Kara no Shoujo series.

Ryouichi's childhood was overshadowed by an older brother, leading to abuse from his father. Tragically, his sister Eriko took the brunt of this abuse, culminating in her current condition. He relentlessly strives for promotion to prevent others from suffering the same fate as his sister.