Sanjō made his anime debut in 1986 as screenwriter of the MD Geist OVA. The following year he would publish his first manga, Skybomber Chokusen, and would largely remain in this field for many years (both as a creator and as an article writer for manga magazines). He began to shift back to the television sphere after he was scouted as writer for the 2005 Gaiking: Legend of Daiku Maryu, which would also lead to him branching out into a number of tokusatsu titles.
Sanjō is also known to write under the Pen Names of Sutaruhinnote and Ryuu Sagawanote .
Works with Sanjō as sole or head writer include:
- Amaenbou Z
- Beet the Vandel Buster
- Cremators (as Ryuu Sagawa)
- Cybernetics Guardian
- Digimon Adventure (2013 videogame)
- Digimon Xros Wars (anime)
- Dragon Quest: The Adventure of Dai
- Dragon Quest I Hiden: Ryuou Baribari Tai
- Dragon Quest IV Gaiden: Jigoku no Meikyuu
- Ephemeral Fantasia
- Gaiking: Legend of Daiku Maryu
- GeGeGe no Kitarō (2007 anime)
- Guilts the Sun Blade
- The Guyver: Bio-Booster Armor (1989 OVA; first half of the series)
- Jaseiken Necromancer
- Kamen Rider Drive (29 out of 48 episodes)
- Kamen Rider × Kamen Rider Drive & Gaim: Movie War Full Throttle (Drive act and Movie War Full Throttle act)
- Shuriken Sentai Ninninger vs. Kamen Rider Drive
- Kamen Rider Drive: Surprise Future
- Kamen Rider Drive Saga: Kamen Rider Chaser
- Kamen Rider Drive Saga Kamen Rider Heart
- Kamen Rider Drive Saga: Kamen Rider Brain
- Kamen Rider W (25 out of 49 episodes)
- Kamen Rider × Kamen Rider W & Decade: Movie War 2010 (W act)
- Kamen Rider W FOREVER: A to Z/The Gaia Memories of Fate
- Kamen Rider × Kamen Rider OOO & W feat. Skull: Movie War Core (W act and Movie War Core act)
- Kamen Rider W Returns: Kamen Rider Eternal (also plays the Sweets Dopant)
- Kamen Rider W: Successor of Z
- Fuuto P.I.
- Kousendou ga Iku!note (as Ryuu Sagawa)
- Lovey Dovey Star!note (a rare Shōjo title)
- MD Geist (1986 + 1996 OVAs; screenwriter debut)
- Piece ~Fragments of a Memory~
- Sideborne
- Skybomber Chokusen (manga debut)
- Ultraman Super Fighter Legend (first manga + anime; as Ryuu Sagawa)
- Zoku Zoku Heroes
- Zyuden Sentai Kyoryuger (every episode, a rarity in toku)
- Zyuden Sentai Kyoryuger: Gaburincho of Music
- Zyuden Sentai Kyoryuger vs. Go-Busters
- Zyuden Sentai Kyoryuger Returns: 100 YEARS AFTER
Other works he has contributed to include:
- Cutie Honey: THE LIVE (13 episodes)
- Garuda Bima-X (11 out of 50 episodes)
- Kamen Rider Fourze (18 out of 48 episodes)
- Kamen Rider Zero-One (guest writer for episodes 12 & 13)
- Mahou Sentai Magiranger (developed the setting's magic system; uncredited)
- Mashin Sentai Kiramager (episodes 7, 8, 17 & 18)
