Yasuo

Before the murders began, Yasuo and Hikari were in a relationship. Those who knew them say that Hikari was insanely dependent on Yasuo.

Yasuo studies at the same university Hikari attended, that's where they met, but Yasuo isn't very diligent with his studies.

Koichi has paid him several visits since he tracks down Bloody Yuki, but he hasn't gotten anything out of him despite the fact that he thinks he's hiding something.