Hotaru Hinase is a first-year high school student who treasures her family and friends above all else. Unable to understand romance, she decides she will be content living without the experience of falling in love.

While Hotaru is spending time at a cafe with her close friend, she witnesses the relentless breakup of a handsome honor student, Hananoi. Encountering him sitting alone in the snow on her way home, she extends her umbrella to him in a gesture of kindness.

The very next day, Hananoi appears in Hotaru's classroom, asking her to be his girlfriend. Despite being rejected, Hananoi sticks closely by Hotaru's side, performing selfless acts in hopes of pleasing her. Hotaru begins to feel emotions she had never felt before. Believing that these emotions could blossom into love, Hotaru agrees to date Hananoi.

Hananoi-kun to Koi no Yamai was published digitally in English as A Condition Called Love by Kodansha USA from March 3, 2020, to February 10, 2026, and in print since January 24, 2023.

In 2021, the series won the 45th Kodansha Manga Awards in the shoujo category.