Keith, lead singer of the band Zero Sum, harbors an intense romantic obsession with his brother—Yuuka's partner. This obsession fuels his every action.

He orchestrates a scheme against Yuuka, leveraging his position to arrange backstage passes for her and his brother to a Zero Sum concert. After the show, he facilitates Yuuka's kidnapping by the other band members, deliberately removing himself from direct participation. The band members then rape Yuuka on a rooftop as part of Keith's calculated plan.

His objective is to inflict trauma that irrevocably severs Yuuka's relationship with his brother, driven by possessive desire. The scheme achieves its immediate goal: Yuuka is left psychologically scarred, unable to escape the trauma's grip.