Yuu

Kuchisake-onna, a slit-mouthed youkai.

In reality, it's a spirit of a crossdresser who committed suicide after being two-timed by his boyfriend. He actually didn't mean to die, it was all a ploy to get back with his boyfriend that backfired spectacularly. He phoned his boyfriend, believing that he will save him in time, and cut his wrist while awaiting his arrival, but the man didn't care to show up, too busy fooling around with his other lover. To add insult to injury, he never even went to the funeral.

The red thing around Yuu's mouth isn't blood, but lipstick, a gift from the unfaithful boyfriend which he smeared on his face out of spite. The lipstick is a manifestation of his resentment towards his boyfriend and it disappears after he promises to visit Yuu's grave.

Yuu haunts the boys' locker room. His ghost power is possession.