If I were to choose just one favorite Japanese literature available online, I would pick Midori Osaki’s Wandering in the Realm of the Seventh Sense (it is legally uploaded on MUSE).

https://muse.jhu.edu/article/609543
*the first few pages are introduction and the main text starts with “Some time...”

With an abundance of obscure and beautiful imageries ,this stands out in my memory as a one-of-a-kind masterpiece in the field of fantasy literature. Additionally, a myriad of Japanese writers, including Mieko Kawakami and Osamu Dazai, applaud her works.