Natsu e no Tobira

 is a 1975 Japanese manga by Keiko Takemiya. It is an early example of a shōnen-ai manga. It was originally serialized in "Hana to Yume", published by Hakusensha, and it was re-released in 2000 by Kodansha. An animated film version of this manga was released on March 20, 1981 in Japan.
Manga.
The original manga of "Natsue no Tobira" is a short story, which first appeared in 19th and 20th issues of magazine "Hana to Yume" in October 1975. This work was contained in the anthology book of Keiko Takemiya, published in 1976. In 1981, a 60-minute anime movie adaptation was released in Japan.
The plot is a coming-of-age tragic romance involving five children in a French academy: a young boy Marion begins an affair with an older woman; his friend Ledania has unrequited feelings for him; their friend Claude is secretly deeply in love with Marion; friends Lind and Jacques develop a dangerous rivalry over their love for Ledania.