Hinata Sunohara is the main protagonist of the series. He is a young Japanese high school student who lives alone in a Tokyo apartment after his parents died in a car accident when he was a child. He carries the emotional weight of this tragedy, feeling a sense of guilt because he had momentarily distracted his father while he was driving just before the crash. This traumatic experience forged his core personality: a deep-seated conviction that he must protect others, even if it means sacrificing his own well-being. This selfless and kind-hearted nature is exactly why he was chosen to be summoned to another world to act as a hero.

During his time in the fantasy realm, Hinata became a crucial fighter in the adventuring party that ultimately vanquished a powerful Demon Lord. His party included a dark elf named Mariabelle, who became deeply infatuated with him. Upon the Demon Lord's defeat, Hinata was immediately sent back to Earth, leaving his otherworldly life behind. He attempted to settle back into his normal routine, but his past followed him when Mariabelle suddenly teleported into his apartment, stark naked, to confess her love and live with him forever. True to his compassionate nature, Hinata agreed to let her stay and help her acclimate to modern human society.

A significant portion of the story revolves around Hinata's relationship with Mariabelle. He genuinely cares for her and, over time, comes to realize that he reciprocates her feelings. However, he is constantly caught off guard by her blatantly aggressive and obsessive behavior, which leaves him extremely flustered. His more traditional and pure sense of love often clashes with Mariabelles unrelenting, yandere-style pursuit, creating the central comedic and dramatic tension of the narrative. The situation is further complicated by the fact that he interacts with other girls, such as his classmate Sakura Mochida, which triggers Mariabelle's murderously jealous side, putting Hinata in a position where he must manage her extreme reactions while navigating his daily life. One of his notable practical abilities is that he is a skilled cook, a talent that proves useful when caring for his new, otherworldly roommate.