Shinobu Hisatake, known as Shinobu-kun, is Suzu Naito's childhood friend and classmate. Acting as her self-appointed protector following her mother's death and subsequent withdrawal, he maintains a close yet complex relationship with Suzu. Shinobu displays consistent concern for her well-being as she contends with social anxiety and trauma.

His protective nature translates into both physical and emotional support. Shinobu persists as a steady presence in Suzu's life despite her emotional distance, frequently intervening during moments of social pressure or distress. This dynamic continues even as Suzu engages with her dual identity within the virtual world of "U".

Unspoken romantic feelings exist mutually between Shinobu and Suzu, though neither voices them explicitly. Suzu attempts confession twice: once interrupted by their classmate Kamishin, and again when Shinobu inadvertently exposes her identity as Belle during a confrontation. Shinobu's own feelings remain ambiguous, yet his actions consistently suggest profound care extending beyond friendship.

Shinobu plays a direct role in Suzu's critical mission to aid Kei and his brother, assisting in locating the abused siblings. He later acknowledges Suzu's courage in confronting their father. Following this event, Shinobu expresses pride in her growth, observing she no longer requires his protection. This realization motivates him to openly pursue a romantic relationship with her, signaling a definitive shift in their dynamic.