Akihiro Kaji is the male lead of the story and holds the position of the ace in his company's sales department. On the surface, he is admired by his colleagues for being good-looking, charming, and highly competent. However, this polished public image conceals a deeply narcissistic personality. In private, Kaji is a cynical playboy who looks down on others and maintains a secret scoring system, rating people based on their attractiveness and sexual desirability. The author of the original manga has described him as a "coward in reality" who feels "lonely" inside, suggesting his arrogance is a defense mechanism against genuine emotional vulnerability.

Kaji's backstory reveals the origins of his guarded and promiscuous lifestyle. During junior high school, he played basketball and first became aware of his attraction to men after seeing a model in a magazine, a realization that frightened him. His parents had a troubled marriage, and his mother left when he was a child, which likely contributed to his cynical view of relationships. He briefly had a girlfriend in high school, but after graduation, he began accepting dates from men, though he found he did not develop romantic feelings for any of them. By the age of twenty, he started frequenting gay bars and concluded that love was not something he needed, settling instead for a series of casual flings.

His primary motivation throughout the story is to find a perfect sexual partner who meets his impossibly high standards, all while avoiding any real emotional connection. This detached and transactional approach to intimacy is challenged when he is paired with Yu Fukami, a bland and unassuming colleague from the IT department, on an overnight business trip. Initially, Kaji finds Fukami sloppy and uninteresting, mentally ranking him as the lowest possible score. However, his perception is shattered when he sees Fukami emerging from the shower without his glasses, revealing an unexpectedly attractive and erotic side. This discovery forces Kaji to confront an attraction he cannot rationalize or dismiss.

The central relationship is with Yu Fukami. What begins as a physical provocation evolves into a friends-with-benefits arrangement, with Fukami setting the condition that Kaji cannot fall in love with him. This dynamic becomes the engine for Kaji's development. As he spends more time with Fukami, his shallow scoring system and narcissistic worldview begin to erode. He experiences genuine emotions like jealousy when other colleagues take an interest in a more polished version of Fukami, and he finds himself wanting to keep Fukami to himself, a stark contrast to his previous detached lifestyle. Kaji's journey involves a slow and often reluctant surrender to the feelings he develops, moving from a man who saw people as numbers to someone capable of emotional vulnerability.

Kaji's notable abilities are tied to his professional persona and his deceptive nature. He is highly skilled at his sales job, which requires the charm and social grace he exhibits publicly. He is also adept at maintaining a double life, seamlessly presenting a friendly and helpful exterior while harboring condescending and calculating private thoughts. His ranking system, while a character flaw, demonstrates an obsessive and analytical mind, though it is a trait he ultimately abandons as he grows closer to Fukami.