Mika Tahara wants nothing more out of her high school experience than to have a fleeting romance. But while her friends have quickly matured at the start of the new school year, Mika's childish demeanor does not appeal to any of the boys in her grade. Just as her enthusiasm falters, the naive girl crosses paths with Hiroki "Hiro" Sakurai—one of the school's delinquents.

Though Hiro is rough around the edges, Mika soon falls head over heels for him, and the two start dating. While the relationship seems like everything Mika imagined it would be, jealousy, deceit, violence, and tragedy threaten to tear the two teenagers apart. As they work through these new struggles alongside the volatility of young love, Mika and Hiro find they may have bitten off more than they can chew.

Koizora: Setsunai Koimonogatari was adapted into a Japanese live-action film that was released on November 3, 2007. The manga was also adapted into a television drama series that aired on TBS from August 2, 2008 to September 13, 2008.