Koyomi Hidaka and Shiori Sato meet at his father’s research center and begin to fall in love, but so do their parents, who eventually marry. To avoid becoming stepsiblings, they decide to run away to a parallel universe. Traveling between dimensions is common in their world, but not without repercussions. Does a universe exist for the young couple, and what will it cost them to find it?

While struggling to make friends after his parents’ divorce, Koyomi Takasaki meets Kazune Takigawa, but apparently, they already have. Kazune reveals that she’s from World Line 85, an alternate universe in which she and Koyomi are lovers. But in a reality where moving between dimensions is natural, could Koyomi be the one from another world?