Shirosaki Shizuru shares a room with Kazunari Usa at the Kawai Complex, where he has resided for four years. By profession, he writes novels under the pen name Shizuru-sensei, supplementing his income with part-time work.

Shirosaki possesses a complex personality. He exhibits masochistic tendencies, actively seeking out and enjoying physical harm or verbal abuse, particularly from Mayumi Nishikino, and willingly allows himself to be used for others' emotional relief. Concurrently, he displays overt perversion, including looking up skirts and vocalizing attraction to specific female features. However, he strictly adheres to a personal code forbidding romantic or sexual interest in girls under eighteen, actively discouraging such attention even when directed at him, as occurred with Chinatsu's initial crush.

Beneath these traits lies a fundamentally kind and helpful nature. He proactively crafts intricate items or devises games to alleviate boredom or lift the spirits of fellow residents. Shirosaki listens attentively to problems and offers thoughtful advice. His crafting expertise extends to complex knots and bondage equipment. He generally maintains a friendly, cooperative demeanor with residents like Sumiko, whose occasional punishments align with his preferences.

His past includes a notable school incident: knocked unconscious during gym, he awoke with his hands on a female teacher's chest, earning him the enduring nickname "T-man". He pursued novel writing after high school graduation.

Relationships define his dynamics. Mayumi Nishikino frequently beats him or exploits his masochism for stress relief, which he welcomes. Their ambiguous relationship includes moments suggesting potential underlying affection from Shirosaki, like giving her a piggyback ride home. Later developments hint at him possibly developing genuine feelings, though their connection remains unresolved. His involvement with elementary student Chinatsu began when he helped recover her lost wallet, sparking her intense attachment. Discovering her sadistic side delighted him, but he discerned the root of her fixation, helped resolve her personal issues, leading to significantly reduced visits.

Shirosaki harbors hidden depths. He is a skilled writer whose work is secretly admired by Ritsu Kawai, unaware of his authorship. He occasionally imparts wisdom, serving as an older figure within the complex. His disheveled, outwardly perverted appearance often leads to him being mistaken for a suspicious character, resulting in frequent police detentions outside the complex.