Kouta's world just got turned upside down. His dad's remarriage meant a new stepsister, Aika, and from their first encounter, it's clear she's everything he isn't. By day, Aika effortlessly plays the "perfect angel" for her parents, but behind closed doors, she's a cheeky teenager, a complete mismatch for Kouta. Their personalities clash violently, sparking arguments the moment their eyes meet. They might just be the world's worst siblings, locked in a constant battle of wills. Despite an incredibly rocky start, a subtle shift begins. Beneath Aika's wild exterior, a flicker of interest starts to grow for her caring brother. (Source: Coolmic) Note: Episode 1 received an advanced distribution on AnimeFesta on December 12th, 2025. The start date reflects the start of the regular series broadcasting.