Yū Kashima enters Morimori Academy as a first-year transfer student alongside Takashi Toono. Drawn by its name, he joins the Photography Club expecting a focus on photography, only to discover its actual purpose is providing sexual services to students. Yet he remains with the club, finding potential enjoyment in its activities. Standing 178 centimeters tall with a muscular, athletic build from his middle school basketball days (ended by injury), Kashima weighs 70 kilograms. He possesses short, messy dark hair, deep grey eyes, and somewhat tanned skin dotted with faint freckles. His typical school uniform consists of a white collared shirt – often with top buttons undone – layered under a dark sweater, black pants, and red-and-white uwabaki slippers, usually omitting the standard red tie. Kashima's personality radiates consistent outgoingness, friendliness, and kindness. He is nearly always smiling, projecting a charismatic presence that lifts the spirits of those around him. He demonstrates appreciation for everyone and has never expressed hatred. Though occasionally childish or naive, his intelligence is evident in his fifth-place class ranking. He shows understanding and compassion, cheerfully accepting changed plans like missed study sessions with Toono. He grew up as the third of five siblings in a large family, resulting in a dislike of being alone. His older sister, two years his senior, has children, making him an uncle. His cousin, Kyōsuke Yaguchi, harbors longstanding jealousy towards Kashima's natural likability and the admiration he receives, including from a girl Yaguchi once liked. A significant development is his relationship with Toono. To avoid the club's mandatory monthly sex quota and its associated gangbang punishment, Kashima proposes a pretend relationship. This pretense leads him to develop genuine romantic feelings for Toono, whom he considers "beautiful," creating tension within the club and complicating Toono's separate crush on Yaguchi. Kashima's hobbies include taking and viewing photographs, aligning with his initial club interest. He retains basketball skills despite no longer competing. His favorite food is pudding, while he dislikes konjac. He also expresses a particular fondness for flowers, especially lilies (yuri).