Onecha.

When Momoka’s mother and Touri’s father decide to marry, the two young individuals are suddenly thrust into a shared household. Overnight, they transition from being complete strangers to becoming step-siblings, bound together by their parents' new union. Forced to navigate this unexpected change, they must learn to coexist under the same roof while adjusting to an entirely new family dynamic that neither of them chose. As the years pass, Momoka and Touri grow up side by side, sharing the everyday experiences and quiet moments that come with living in the same home. What begins as a standard familial bond between a newly formed brother and sister gradually starts to shift in ways neither anticipated. The comfortable boundaries of their sibling relationship begin to blur, giving way to unfamiliar emotions and unspoken tensions. This slow transformation leaves both of them facing a deeply personal dilemma. As their feelings evolve beyond the conventional expectations of step-siblings, they are forced to confront the changing nature of their connection. Navigating these complicated emotions challenges everything they thought they understood about their family, their roles, and each other, setting the stage for a delicate and emotionally complex journey.