Futago no Danjo ga Wakaranai

During his childhood, Takushi Hatsujou spent his days playing alongside a pair of twins—a brother and a sister. Over time, he developed deep feelings for the sister, eventually working up the courage to propose to her as they grew older. She happily accepted, but their joy was short-lived. For ten long years, circumstances kept the couple apart, as Takushi struggled to secure his grandfather’s approval for the union. Only after finally obtaining that hard-won permission is he allowed to reunite with his beloved. However, the reunion brings an entirely unexpected complication. When Takushi finally sees the twins again, he is stunned to discover that both siblings now present themselves as girls. He quickly realizes that one of them must be cross-dressing, yet their appearances are so remarkably similar that distinguishing between the two has become nearly impossible. Now faced with an extraordinary dilemma, Takushi must figure out which twin is truly the woman he loves and which is her brother in disguise, turning what should have been a joyful reunion into a bewildering challenge.