At first, Taiyō Mitsuboshi is portrayed as a polite, kind, and helpful young man. He warmly welcomes Satō Matsuzaka on her first day at Princess Imperial and assists her with learning the job. Quick to develop feelings for Satō, he confesses to her after only a day, though she promptly rejects him.

Following his assault at Princess Imperial, Mitsuboshi’s personality begins to unravel. He becomes emotionally unstable and paranoid, particularly fearful of adult women. Although he attempts to maintain the polite and friendly demeanor he once had, his trauma surfaces whenever he is confronted by older women, leaving him anxious and shaken. His encounter with Shio Kōbe’s missing person poster sparks an unhealthy fixation; captivated by her innocence and small stature, Mitsuboshi becomes obsessed with the belief that Shio could “cleanse” his tainted soul and help him overcome his fear.

Taiyō Mitsuboshi is considered attractive by many of the girls around him. He has short blond hair, accented by two red hairclips on the right side, and striking blue eyes.

Mitsuboshi is typically seen in two main outfits, A white dress shirt paired with a red necktie, black pants, black shoes, and a green blazer featuring a purple plaid collar. At home, he dresses simply in a T-shirt and sweatpants.

Little is known about Taiyō Mitsuboshi’s early life, though it is noted that his mother cares deeply for him—a fact Shōko Hida once remarked on, wishing for a family as supportive as his. When Satō Matsuzaka began working at Princess Imperial, Mitsuboshi was impressed by her diligence and quick understanding of her duties. He confessed his feelings for her the next day, but she rejected him. Despite this, Mitsuboshi remained admired by many of his female coworkers, who were surprised Satō turned him down.

Out of jealousy toward the attention Mitsuboshi and others gave Satō, the manager of Princess Imperial coerced Mitsuboshi into her office, where she sexually assaulted him, tied him up, and held him captive in the closet for several days. His ordeal ended only after Satō blackmailed the manager using video evidence of her confession, securing his release.

The trauma left Mitsuboshi feeling “dirty” and incapable of redemption. His obsession with purity took root when he came across a missing person flyer for Shio Kōbe. Enchanted by Shio’s innocent image, he became convinced that she could cleanse his soul. His fixation deepened after meeting Shio briefly in the city, leading him to hoard her missing flyers and fantasize about keeping her for himself.

Upon learning that Satō was harboring Shio, Mitsuboshi schemed with her to remove Asahi Kōbe, hoping that doing so would earn him access to Shio. Proclaiming himself Shio’s “knight,” he attempted to help Satō by dealing with Asahi, though his true motives were selfish.

Eventually, Mitsuboshi tried to take Shio for himself by racing to Satō’s apartment, only to find the door locked. There, Satō’s aunt deceived him, offering to open the door but instead assaulting him. While tied up, he answered Asahi’s call and pleaded for help, but Asahi, fed up with Mitsuboshi’s lies, abandoned him.

In the manga’s final scenes, Mitsuboshi is shown leaving his house with his mother calling after him. He smiles, telling her “It’s okay,” implying he feels cleansed. In contrast, the anime shows him at the end on his knees in his room, visibly defeated and traumatized, with his fate left uncertain.

Satō Matsuzaka
Mitsuboshi and Satō initially shared a friendly relationship during their time working together. However, after Mitsuboshi became obsessed with Shio Kōbe, Satō’s attitude toward him shifted. Recognizing his fixation, Satō manipulates Mitsuboshi by offering him the chance to see Shio again if he helps eliminate a threat to her. Driven by his trauma and obsession, Mitsuboshi agrees and becomes her accomplice. In the end, after being assaulted by Satō’s aunt and calling for help as the apartment burns, Satō ignores his pleas, showing she no longer cares for him.

Shio Kōbe
Mitsuboshi’s only direct interaction with Shio occurs when she escapes the apartment in search of Satō. Seeing this as his chance, Mitsuboshi asks Shio to “kiss his boo-boo” to heal him. Shio, confused, pats his head gently. Mitsuboshi, believing this contact purifies him, contemplates taking her home to keep her close. Before he can act, two thugs attack him, triggering a psychological breakdown in Shio. Satō arrives, subdues the thugs, and takes Shio home. This brief encounter fuels Mitsuboshi’s obsession.

Asahi Kōbe
Mitsuboshi initially shows kindness toward Asahi, saving him from thugs and bringing him to Cure á Cute. However, as Mitsuboshi’s obsession with Shio deepens, he begins withholding information about her at Satō’s urging. Asahi grows suspicious and resentful, equating Mitsuboshi’s deceit with the betrayal he associates with untrustworthy adults. Mitsuboshi lies to Asahi, falsely claiming that Satō and Shio have already fled, and shows him Shio’s sock as “proof.” During the apartment fire, Mitsuboshi pleads for Asahi’s help, but Asahi abandons him, unable to forgive his betrayal.