The story of Kodomo no Jikan is centered around 23-year-old Aoki Daisuke, who has just landed his first teaching job as a grade school teacher at Futatsubashi Elementary School. He is placed in charge of Class 3-1, where one of his students, a mischievously precocious Rin Kokonoe, develops a crush on him and goes so far as to proclaim herself Aoki's girlfriend. She aggressively pursues her efforts to be with her teacher despite the fact that he will lose his job if she gets too close, a situation further complicated by the often complex, intertwining relationships existing between them and their respective friends, families, and peers.

In 2007, Seven Seas Entertainment licensed Kodomo no Jikan for North American distribution under the title Nymphet, but controversies surrounding the manga's content led to the project's cancellation. In 2016, Digital Manga Inc. launched a successful Kickstarter campaign to publish the series in five omnibus volumes. However, Digital Manga Inc. president Hikaru Sasahara later stated in March 2018 that the company had run into a "weakened" financial situation. The project has yet to be completed.