Ranmaru Ōmi, third-generation head of the Ōmi yakuza clan, enters a politically brokered marriage with Kaoru, a childhood acquaintance and scion of a rival faction. Designed to cement alliances, the union fractures swiftly under mutual resentment, climaxing when Kaoru banishes him from their cabin mid-honeymoon aboard an Italian cruise liner.

Amid the fallout, he crosses paths with Alberto Valentiano, a Japanese-speaking Italian captain, following a bar brawl against antagonistic yakuza. Alberto’s intervention sparks a liquor-fueled liaison that deepens into intimacy, catalyzing Ranmaru’s struggle between clan loyalties and growing feelings for the foreigner.

His yakuza upbringing forges a hardened exterior—brash, guarded against weakness—yet Alberto’s influence chips at these defenses, exposing unexpected emotional candor. Even within his criminal world, Ranmaru unwittingly garners male admirers beyond romantic contexts, a pattern echoing through his relationships.

Later, Kaoru severs their marriage to release him from obligation, clearing his path toward Alberto. This liberation underscores Ranmaru’s shift from duty-bound heir to self-driven individual, though his actions remain tinged with the impulsivity and wariness ingrained by yakuza life.

Supplementary manga arcs trace his tempered abrasiveness over time, framing his evolution through the push-pull of familial duty versus personal yearning, all entangled with underworld machinations and a transcontinental romance.