The ordinary daily life of Yotsuba Fu, a college student with zero romantic experience, is suddenly turned upside down one day. The senior admired by everyone on campus, Kogami Sara, abruptly tells him that he is someone who came from a parallel world, and that "we are lovers", declaring it unilaterally. Confused by this sudden confession from Sara, with whom he has never even exchanged words before, Fu nevertheless finds himself gradually drawn to him. However, he soon begins to suffer from the inner conflict that he himself is not the Fu whom Sara loved in that parallel world. At the same time, Sara is also carrying a major secret of his own… Guided together by the threads of fate, what path of love will the two ultimately choose?
