He is best known as the creator of Sword Art Online and Accel World, both of which have been adapted into anime series.

Kawahara wrote the first volume of Sword Art Online in 2001 as a competition entry for the 2002 ASCII Media Works Dengeki Game Novel Prize (電撃ゲーム小説大賞, Dengeki Game Shōsetsu Taishō, now Dengeki Novel Prize), but refrained from submitting it as he had exceeded the page limit; he instead published it as a web novel under the pen name Fumio Kunori (九里史生, Kunori Fumio).

[3] Over time, he wrote more main arcs and side stories, which were later updated for light novel publication.

[13] After gaining fame from the Dengeki award, Kawahara republished Sword Art Online in print.

[22] In 2022, Kawahara started publishing a new light novel series, titled Demons' Crest, with illustrations by Yukiko Horiguchi.