Akaneiro ni Somaru Saka follows Junichi Nagase, an ordinary student whose carefully ordered life is disrupted after he rescues Yuuhi Katagiri, the sheltered daughter of a powerful family, from a street attack. Junichi tries to brush off the encounter, but the next day Yuuhi transfers into his class and calls him the "Geno Killer," the only name she remembers. Their awkward reunion is bad enough on its own, yet rumors spread even faster when a misunderstanding leads Junichi to kiss her.
What should have been a fleeting embarrassment turns into a much bigger problem when Junichi learns that he is actually Yuuhi's fiancé. Yuuhi wants nothing to do with a marriage she never chose, and she cannot openly defy her father's decision. As a result, she moves into the house Junichi shares with his little sister Minato, determined to prove that he is unfit to be her husband.
Living under the same roof forces Yuuhi and Junichi to argue, clash, and slowly see sides of each other that neither expected. Akaneiro ni Somaru Saka blends romantic comedy, pride, and everyday school-life tension as their relationship shifts from hostility to something far harder to ignore. Between class gossip, family pressure, and their own stubborn personalities, both of them are pushed toward a choice neither is prepared for: keep fighting, or admit the feelings growing between them.