The story of Hantsuki focuses on the budding relationship between Yuichi Ezaki and Rika Akiba. Both teens are hospitalized in Yuichi's home town hospital for their respective conditions. Yuichi has hepatitis A which can be cured with rest, while Rika has problems with a weak heart valve (cardiomyopathy, to be exact) that can only be cured with a risky operation. These teens would then fall in love while they spend time with one another.