The dark secret hidden within happiness... One day, Koji gathers his courage and confesses his feelings to Chiharu, his next-door neighbor. Accepting his confession, the two begin a romantic relationship. Touched by Koji's pure heart, Chiharu gradually opens up, and they build a loving bond as partners. Their innocent, warm affection for each other grows deeper with time. But suddenly, their blissful days are overshadowed by a dark cloud. Chiharu's past is revealed, shocking Koji to the core. Their relationship can no longer remain simply happy... This truth sparks a new drama.