Natsuki Sakaki, the soft-spoken bassist of idol unit High×Joker, carries a quiet presence marked by introspection and unwavering loyalty to childhood friend Jun Fuyumi. His reserved nature leads him to retreat into observation during social interactions, relying on Jun or trusted companions to navigate unfamiliar settings. Even among friends, his speech remains measured and sparse, reflecting a preference for listening over speaking.

A childhood accident involving Jun, which permanently halted Jun’s piano career, anchors Natsuki’s guilt-ridden devotion to him. This guilt motivated his entry into High×Joker after Jun expressed interest in the group, and his commitment to the unit revolves around staying near Jun to safeguard their bond and preserve the music tied to their shared past. Despite unintentionally drawing attention for his striking appearance and quiet magnetism, Natsuki remains oblivious to the admiration he garners.

Beyond Jun, his relationships reveal layered loyalties: a kinship with Hirata forged through mutual hardships, disdain for Yuto Ijika over Yuto’s role in Rokuro’s tragic fate, and guarded alliances with reserved peers like Ayanokoji and Itona. His animosity toward Makoto Itou stems from Makoto’s abandonment of Sekai, someone Natsuki deeply valued.

Within Sora’s team, Natsuki assumes a subtle yet pivotal role as a mediator, channeling his empathy to defuse tensions and shield those he cherishes. His actions consistently mirror a protective instinct shaped by guilt and a silent vigilance over the emotional landscapes of others.