Sōsei Arakida is a detective defined by his intimidating presence and unsettling rumors, which fuel his preference for solitary investigations. He stands 180 cm tall at 27 years old, with silver hair and distinctive mint green eyes, born on May 23.

Contrasting his fearsome reputation, he harbors a deep fondness for literature, openly declaring himself a devoted fan of novelist Makoto Tsuzuki. Privately, he wears unfashionable wireframe glasses at home.

His communication is consistently terse and direct, minimizing social interaction. He questions the necessity of conversation, stating, "Is conversation really that important?" and asserts that efficient thought conveyance suffices. This bluntness surfaces in sample dialogue: "Arakida Sosei, a police officer. What? This should be enough for a self-introduce."

Despite this abrasive exterior, he displays unexpected attentiveness to small natural details, such as warning someone to avoid crushing a flower: "...It’ll be a pity if you step on it..."

Questionnaires specify his preferences: his favorite book is by Tsuzuki-sensei, his sport of choice is basketball, and his favored celebrity is actor Tsuzuki Kyosuke. When asked about holidays, his response is unequivocal: "I work."