[5] He debuted with his novel Ayakashigatari (あやかしがたり) in May of the same year, which won the 3rd Shogakukan Gagaga Bunko Light Novel Award.
In March 2011, the first volume of his most known work, My Youth Romantic Comedy Is Wrong, as I Expected, was published by Gagaga Bunko.
Dōdemo Ii Sekai Nante: Qualidea Code, a further novel written by Watari, was released during the airing of the anime.
[9] He is close friends with fellow light novelists Sō Sagara and Kōshi Tachibana; together, they formed the writing group Speakeasy.
[8] Watari is also close friends with voice actors Takuya Eguchi and Chado Horii, and has participated in their event Eguwatachado and DVD.