The series was conceived around September 2014 by producer Ken Minami and director Seiji Kishi, who wanted to create a realistic human drama, and the concept shifted to a romance after being influenced by the film 'Tamako Love Story'.

The setting was deliberately chosen to be neither a big city nor the countryside; Kawagoe was selected because it was not far from Tokyo and easy to scout for filming locations.

Third-year junior high school students were chosen as protagonists instead of the more common high schoolers, because that age still carries the constraints of school and family life.

Character designer loundraw, known for illustrating the Hayakawa Bunko JA science fiction book covers and the artwork for 'I Want to Eat Your Pancreas', was brought in specifically because the staff felt a typical bishōjo-anime style character design would not fit the show.

Unlike most anime, the series was produced using pre-scoring (voice recording before animation) rather than the usual post-recording (aftre-reko), with all cast recordings starting in August 2016 completed before the first episode preview screening on March 20, 2017.

The show's logo was created by deconstructing and reassembling handwriting samples collected from an entire real class of third-year junior high school students, with light blue representing Kotaro and pink representing Akane.

Each episode's subtitle is named after an actual work of Japanese literature or poetry.

The anime's ending sequence featured LINE chat screens between a boy and girl each week, which was revealed in the finale to be messages between an older, grown-up Kotaro and Akane; the same final episode's ending also depicted the couple's long-distance relationship, marriage, and the birth of their child through still images.

Writer Ohyama Kumao described the show as a 'late-night love-terror anime' after noting that viewers' anguished screams flooded Twitter timelines during broadcasts, a description the official anime Twitter account embraced by promoting the hashtag '#koitero' (love terror).

Voice actress Konomi Kohara (Akane) frequently promoted the charms of Kawagoe on her radio show and social media after starring in the series, boosting pilgrimage tourism to the city, and was appointed as a 'Koedo Kawagoe Tourism Goodwill Ambassador' by Kawagoe City in February 2026.