Tonkotsu

A girl Sakurai meets after he murders those bullying him at his school, the two met online and but decided to meet in person. They find an interest in each other and have begun dating. Tonkotsu also knows Sakata, they don't show together too much, but they seem like friends, probably due to Sakurai being a mutual friend. Tonkotsu also gets kind of involved in Gantz related cases, without actually knowing about Gantz. She meets Sakurai in Shinjuku [She also meets Sakata a few minutes later] at the same day Izumi makes his threat come true, starting a massacre in order to go back to Gantz's room. While the three of them run away, she falls and sprains her ankle, telling Sakurai and Sakata to keep running and she'll play dead so they won't worry about her. Sakurai refuses and instead of running, decides that he should try and stop the killer along with Sakata, indirectly making Tonkotsu responsible for their deaths and entrance into the Gantz game.