Misuzu has never known what it means to have a true friend. Raised by a busy father after losing her mother at a young age, she grew up emotionally withdrawn and struggles to form deep connections with others. Her classmate Chizuru faces a different kind of isolation: bright and energetic by nature, she possesses the ability to see beings that do not belong to this world, a trait that causes others to keep their distance. The story is set in contemporary Japan during a single summer that will change both of their lives.

Their unlikely bond begins on the night of a summer festival, when Misuzu is nearly tricked out of her money by classmates. Chizuru appears with a warning delivered from the spirit lingering behind Misuzu, and from that strange encounter, the distance between the two girls begins to shrink. As they spend more time together, they slowly share the worlds they each inhabit. However, Chizuru has been strictly forbidden by the elderly woman who raised her from growing close to others. If Chizuru harbors even the slightest resentment toward someone, that feeling can physically harm them. The more the two girls are drawn to each other, the more they step toward a boundary they were never meant to cross. Beyond that line lies both light and darkness, and soon the two worlds they belong to begin quietly pulling them apart.

The complete original Japanese series, titled Okashiki Sekai no Kyōkaisen, began as a one-shot on Shogakukan's Manga ONE platform where it won an award. Serialization started on the same platform in 2020, and the fifth and final compiled volume was released in August 2021. The narrative spans these five volumes, weaving a quiet, bittersweet tale of two girls, the summer that changes them, and the invisible line between the visible and invisible worlds they must learn to navigate.