Saku lived a normal life with his cousin Kuran, enduring daily torment from his childhood friend, Karin. That changed when a girl named Kiiro appeared out of nowhere, claiming to be the future daughter of Karin and Saku. Convinced she will cease to exist unless Saku and Karin marry, she complicates everyone's lives. The situation grows even more chaotic when Hiiro, a girl claiming to be the future daughter of Kuran and Saku from a different timeline, arrives with the aim of uniting Saku with his cousin. Saku is suddenly confronted with a dilemma: whom should he choose as his wife, and which daughter should he save from vanishing into nothingness?