At the center of Kodomo no Jikan is Aoki Daisuke, a 23-year-old who just began his first teaching job at Futatsubashi Elementary School. Assigned to teach Class 3-1, Aoki must navigate the challenging presence of Rin Kokonoe, a mischievous and precocious student who quickly develops romantic feelings for him, even calling herself his girlfriend. As Rin becomes increasingly persistent in her pursuit, Aoki struggles to maintain his professional boundaries, knowing that any slip could cost him his job. Amidst the complicated relationships between Aoki, Rin, and their wider circles of friends, family, and peers, the story explores the consequences of crossing boundaries, both personal and professional.