Police Officer Yūki is a member of the Tokyo Police force who was stationed at a small police box, together with another colleague, in the same district where Tokiwa lives. Before the ghost incident he regularly took Rein home when she had gotten lost once again.
Kotohiro's father called him and his colleague to help when a ghost appeared in their garden. When they arrived, Tokiwa and Rein were fighting the ghost and Yūki did not hesitate to come to their aid even when his parter tried to stop him from using his weapon.
Because of his bravery and his resolution to protect all citizens even against the supernatural he was promoted by Sennbeiser Suzuki.
- When Yūki was a little child he wanted to become a space detective.