Retto Enjou is a high school student recruited to combat the alien Kiseichuu (Censor Bugs), which drain humanity's erotic energy (H-energy) to cause extinction. Possessing a muscular build and short red hair, he demonstrates a strong sense of justice, dedication to protecting others, and a non-perverted demeanor despite his mission's nature. His combat abilities rely on converting H-energy into power through specialized equipment.

Five years before the main events, an encounter with Censor Bugs altered his childhood friend Kirara Hoshino's personality, making her distant and cold toward him. Despite this estrangement, he maintains deep romantic feelings for her. His persistent efforts eventually rebuild their relationship, culminating in a confession that leads to them becoming a couple.

His family includes a younger sister, Hiro Enjou, and an uncle, Jou Anno. Jou heads the Earth Defence Force's Saitama Branch and recruits Retto into the HxEros team. Retto initially finds Jou's feminine appearance unsettling. As part of the HxEros team, he partners with Kirara and teammates Momoka Momozono, Sora Tenkuji, and Maihime Shirayuki.

Interpersonal dynamics involve accidental erotic situations with teammates, such as Momoka falling on him or Sora sleepwalking into his bed. He also interacts with Chacha, a defected Censor Bug who assists in building his H-energy. His relationships extend to classmates Haruka Itou and Yuuna Asana, including unintended intimate encounters during missions.

Character development centers on his unwavering commitment to both his mission and Kirara. Early efforts to reconnect with her evolve into decisive actions, including a proposal during the manga's events. His journey concludes with mutual acknowledgment of their feelings, resolving their long-standing emotional distance.