Ano Oni Kyoushi ga Boku no Ane ni Narundesuka?

A young boy is thrilled when he learns his father is remarrying, especially since this means he’ll finally have an older sister. His excitement quickly fades, however, when he discovers his new stepsister is none other than Shina, the notoriously strict PE teacher from his school. As his father moves in with his new wife, the boy is left to share a home with Shina alone. To his surprise, the stern and disciplined teacher he knows from school is nothing like the woman he now lives with. At home, Shina reveals a softer side—she’s awkward, terrified of bugs, and unexpectedly warm-hearted. Their daily interactions slowly peel back the layers of her personality, leaving the boy to reconcile the two very different versions of the woman he now calls family. The contrast between her professional persona and her private self becomes a source of both confusion and unexpected bonding. Their shared living space becomes a stage for humorous and heartfelt moments as they navigate their new relationship. The boy finds himself torn between his initial discomfort and the growing affection he feels for his clumsy yet caring sister. Through their time together, he learns that people often hide their true selves behind the roles they play in public. The story explores themes of family, identity, and the masks people wear in different aspects of their lives. What begins as an awkward arrangement gradually transforms into a meaningful connection neither of them anticipated.