What's Behind Two-Floor Love?

Hanada Akihito, a high school student, is forced to adapt to a new living arrangement after his parents' divorce, relocating to his older sister's apartment on the second floor. As he navigates this unfamiliar environment, Akihito meets his sister's friends, including the intelligent and beautiful Natsumi, with whom he forms a study partnership. Through their frequent study sessions, Akihito discovers that Natsumi's charming facade conceals a more complex and intriguing personality, drawing him into a deeper connection with her.