Madoka and Tatsuya, childhood friends who kept their relationship a secret from their parents. The two had wished for their bond to last forever, but it crumbled when their parents remarried, tearing them apart as siblings. Living under the same roof, they felt each other's presence growing distant. A female classmate of Tatsuya's closed in on him during the gaps. Driven by jealousy, Madoka pressured Tatsuya into resuming their physical relationship. The two secretly returned to being lovers. However, their happy time was fleeting; when their parents found out about their relationship, they were urged to break up. Madoka ran away from home, and Tatsuya chased after her. At the seaside where they ended up, the two swore eternal love... Childhood friends who continued secret intercourse without their parents' knowledge—a blue, twisted, and forbidden love story.
