I read this story years and years ago when I first lived in Japan. I haven’t re-read it since, but I remember it blew my socks off. A guy finds a piece of magic chalk and draws a door to another universe on his apartment wall. A bit like that cartoon Penny Crayon.
First published in Japanese 1950. Collected in The Shōwa Anthology: Modern Japanese Short Stories, Kodansha 1992. Available to read online here