Ane no Shinyuu, Watashi no Koibito.

Sena is a novelist whose professional life revolves around crafting stories, yet her most deeply guarded secret remains entirely unwritten. For as long as she can remember, she has harbored quiet, unspoken romantic feelings for her older sister, Yuuna. Keeping these emotions hidden has been a constant struggle, but Sena has always accepted that her affection must remain in the shadows, never to be revealed or acted upon. Everything changes when Sena learns the startling news that Yuuna is preparing to get married. The impending wedding shatters the fragile emotional balance Sena has maintained for years, forcing her to confront the reality of losing her sister to someone else. Amidst this personal turmoil, an unexpected figure steps into her life. Kiku, who is not only Yuuna’s closest best friend but also her former romantic partner, approaches Sena during this vulnerable period with a proposition that defies all expectations. Rather than offering simple comfort, Kiku asks Sena to become her lover. This sudden and intimate proposal pulls Sena into a complicated web of desire, grief, and tangled relationships. Bound together by their shared connection to Yuuna, Sena and Kiku must navigate the emotional consequences of an arrangement born from heartbreak, blurring the lines between consolation and genuine romance.