The Tunnel to Summer, the Exit of Goodbyes (Japanese: 夏へのトンネル、さよならの出口, Hepburn: Natsu e no Tonneru, Sayonara no Deguchi) is a Japanese light novel written by Mei Hachimoku and illustrated by Kukka, published by Shogakukan under its Gagaga Bunko imprint in July 2019.

A manga adaptation, titled The Tunnel to Summer, the Exit of Goodbyes: Ultramarine and illustrated by Koudon, was serialized in Shogakukan's seinen manga magazine Monthly Sunday Gene-X from July 2020 to November 2021, with its chapters collected in four tankōbon volumes.

Kaoru Touno is a high school student in a rural town in Japan who keeps to himself, going home each day on the Oosara-Sugimori train line.

One rainy day, Kaoru meets a soaked Anzu Hanashiro at the train station.

The stack of papers they retrieved was an old manga that young Anzu wrote and was thrown into the trash by her father.

Inside the tunnel, Kaoru finds himself in a fictional space where he reunites with his sister the day after she died, but begins receiving messages from outside, something previously proven to be impossible.

The Tunnel to Summer, the Exit of Goodbyes, written by Mei Hachimoku and illustrated by Kukka, was released by Shogakukan under its Gagaga Bunko imprint on July 18, 2019.

[5] In July 2021, Seven Seas Entertainment announced that they had licensed the light novel for English release in North America.

[7] A manga adaptation, The Tunnel to Summer, the Exit of Goodbyes: Ultramarine (夏へのトンネル、さよならの出口　群青, Natsu e no Tonneru, Sayonara no Deguchi Gunjō), illustrated by Koudon, started its serialization in Shogakukan's seinen manga magazine Monthly Sunday Gene-X on July 18, 2020.

The first part of the final chapter was published on MangaONE on October 1, 2021,[9] and the series finished in Monthly Sunday Gene-X on November 19 of the same year.

[12] In July 2021, Seven Seas Entertainment announced that they had licensed the manga for English release in North America.

The film is produced by CLAP [ja] and written and directed by Tomohisa Taguchi, with Tomomi Yabuki designing the characters and serving as chief animation director, and Harumi Fuuki composing the music.

[29] Writing for The Guardian, Phil Hoad gave the film three out of five stars, describing the plot as simplistic but the animation as "something else", capturing "the momentousness of first love".