When his childhood sweetheart Haru Yobi announces her marriage to a handsome stranger, the protagonist Yumeji Nami feels his destined romance come to an abrupt and shocking end. Tormented by the thought that a confession made on that day, in that place, at that exact moment could have changed everything, he discovers the ability to leap across parallel universes in a desperate pursuit of a happy ending with his first love. The series follows this hopeless romantic as he travels through alternate realities, each representing a different choice or missed opportunity, trying to find the one timeline where his feelings are finally reciprocated.

The narrative explores the concept of parallel worlds not just as a science fiction element, but as a metaphor for the roads not taken in life. As Yumeji repeatedly leaps between dimensions, he encounters other versions of himself from different timelines, all converging at a mysterious café called Kalabi Yau which appears to be a nexus connecting all world axes. His journey is complicated by the presence of Satoyimo, a childhood friend who becomes entangled in his leaps and tries to understand his own feelings as he follows Yumeji across realities.

After successfully proposing to Haru in what seems to be the final timeline, Yumeji finds himself and his beloved pursued by numerous doppelgangers of himself from other parallel worlds. As he races toward a telephone booth that may offer a way out, Satoyimo appears before him, setting up a tense confrontation. The series, serialized in Shonengahosha's Young King Ours magazine since August 2022, has entered its final arc, with the fourth compiled volume released in April 2025. The story builds toward an emotionally intense conclusion that promises to resolve the dilemmas of a young man chasing love across the infinite possibilities of his own life.