- His real name is Tayama Rokuya.
- He was raised on an old-fashioned education and composed poetry and prose in Chinese around fourteen years old. Around a year after that, he also began to learn English and threw himself into both Chinese and English literature.
- He once wrote Ozaki Kouyou asking to become his disciple and sent one sample manuscript. Kouyou criticized the manuscript, but Katai was encouraged to pay him a visit, and after a friendly chat Katai started writing for a magazine edited by an acquaintance of Kouyou's.
- Even early in life, he showed signs of being unable to invent a story, which later manifested in the "confessional" style he started to write in.
- One of his closest and most important friend was Kunikida Doppo, who was opposite to him in personality (Kunikida was cheerful and Katai gloomy) but with whom he could have fun conversing with. It is partly thanks to Kunikida's influence that Katai turned to objective realism, saying "It was why I am able today to confess unabashedly whatever is in my heart".
- In 1902, Katai volunteered to go to China as a correspondent during the Russo-Japanese War, which is how he met Mori Ougai and spent many hours conversing with him.
- His most famous novel The Quilt met extraordinary success. It was one of the first of the confessional "I-novels", whose purpose is to create the impression of authenticity no matter what pain or embarrassment baring the truth may cause. In addition, it was an undisguised confession by a rather well-known author. His later novels also followed this trajectory of being objective and realistic.
- Because of his entire oeuvre forming an entire account of his life, he is the most appropriate to be named as a true Naturalist writer.
- In 1930, Shimazaki Touson, Katai's loyal friend, paid him a visit on his deathbed and asked him what it felt like to die. Katai died only two days later at age 58, due to a cerebral hemorrhage.