To Me, The One Who Loved You

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?