My Girlfriend Cheated on Me, and Now My Flirty Underclassman Won’t Leave Me Alone!

Just days before Christmas, college sophomore Hasegawa Yuuta’s world falls apart when he discovers his girlfriend has been unfaithful. Heartbroken and desperate to avoid the cheerful couples celebrating the holiday season, he retreats into himself, wandering through a festive atmosphere that only deepens his misery. However, his gloomy attempt to hide from the holidays takes an unexpected turn when he literally collides with Shinohara Mayu, a stunning underclassman dressed in a Santa outfit. Rather than leaving him to wallow in his despair, Mayu quickly realizes how entertaining it is to tease her melancholic senior. What starts as playful banter soon evolves into something more persistent, as she begins inventing every possible excuse to insert herself into his daily life. Her relentless, flirtatious attention becomes impossible to ignore, steadily chipping away at his heartbreak. Despite his initial reluctance and lingering pain, Yuuta finds himself swept up in Mayu’s vibrant energy. The miserable holiday he had resigned himself to enduring transforms into something entirely different. Through the warmth of an underclassman who simply refuses to leave him alone, a devastating betrayal gives way to what might just become a Christmas worth remembering.