12-sai.: Chiccha na Mune no Tokimeki

The story begins with Hanabi, a sixth-grade girl who is neither an adult nor a child. She deals with issues such as accidentally witnessing her homeroom teacher kissing, and worrying about experiencing physiological changes before her friends. This is the depiction of a 12-year-old girl's innocent worries and first love.
(Source: Anime News Network)