Tonkotsu

Tonkotsu is caring, direct and unusually accepting of Sakurai despite knowing about his violent past. Her acceptance does not mean approval: she pushes him toward taking responsibility rather than pretending his actions never happened.

She shares Sakurai's interest in using his psychic abilities to find dangerous criminals, treating intervention as a way for him to repay a moral debt. Her influence therefore supports the more compassionate direction he tries to take after meeting her.

Tonkotsu is also brave under immediate danger. During the Shinjuku massacre, an injured ankle leaves her unable to keep running, yet she tells Sakurai and Kenzo Sakata to leave her behind rather than endanger themselves.

Tonkotsu is an ordinary human and possesses no demonstrated psychic abilities or connection to Gantz.

She nevertheless becomes involved in incidents where Sakurai uses his powers. The pair investigate a serial killer together, with Tonkotsu encouraging Sakurai to turn his unusual abilities toward stopping crimes.

Her lack of supernatural protection makes these situations considerably more dangerous for her than for Sakurai.

Tonkotsu enters Sakurai's life shortly after his violent retaliation against his bullies. Their online acquaintance becomes an in-person relationship, and she provides him with companionship during a period dominated by guilt and isolation.

She is present in Shinjuku when Izumi begins his massacre. After injuring her ankle, she urges Sakurai and Sakata to continue without her, but Sakurai instead chooses to confront the killer.

As the predicted Katastrophe approaches, Sakurai chooses to spend what he believes may be his final days with Tonkotsu. During the alien invasion, she is killed while separated from him; discovering her death drives Sakurai into a devastating psychic rampage against the invaders.

Hiroto Sakurai is Tonkotsu's boyfriend. She knows about his past killings and encourages Hiroto Sakurai to use his powers to save people instead, becoming one of his strongest connections to ordinary life.

Kenzo Sakata is Sakurai's psychic mentor and is acquainted with Tonkotsu through their mutual connection to Sakurai.

Shion Izumi indirectly changes Tonkotsu's life when his Shinjuku massacre leads Sakurai and Sakata to confront him and subsequently enter Gantz.