Tsukasa Kiriki is a high school student drawn into Hiroshima's motorcycle gang world, befriending Gokurakucho (Paradise Butterflies) members Yoji, Hisao, and Eiji. His integration into the group culminates in him defeating their leader and rising to become Gokurakucho's eighth leader, pledging to protect its position as Hiroshima's second-strongest gang behind Beast.

His leadership faces an immediate test when Yoji unexpectedly resigns to focus on a part-time job, citing personal reasons. Tsukasa accepts his friend's decision, but Yoji's departure sparks internal tension, particularly with Eiji questioning Tsukasa's judgment. While resolved to uphold his promise to Gokurakucho, Tsukasa privately senses something off in Yoji's demeanor.

Tsukasa's personal life adds strain as his relationship with Kumi frays when she moves to Tokyo for university. She voices concerns about their diverging futures and urges him to consider his own path, highlighting the conflict between his gang responsibilities and broader life aspirations.

The situation escalates with the emergence of rival gang Eden. Tsukasa discovers Yoji has joined Eden and is involved in violent attacks against former allies, including Beast members. This betrayal forces Tsukasa to confront the intensifying gang conflict while navigating the fractured trust within Gokurakucho.

Throughout these events, Tsukasa evolves from an ordinary student into a dedicated leader, driven by loyalty to his friends and a sense of duty to Gokurakucho. His journey intertwines with Hiroshima's volatile underworld, navigating rivalries with top groups like Beast and Nights as he strives to maintain stability.