Karakter utama
Karakter pendukung
Reiji KageyamaPendukung
Tomokazu SekiJepang
Meguro KanetakePendukung
Etsuko KozakuraJepang
Reiko AsagiriPendukung
Mayumi IizukaJepang
Choutarou BanbaPendukung
Takehito KoyasuJepang
Kaoru KonoePendukung
Naoko TakanoJepang
Fei Ling FengPendukung
Chinami NishimuraJepang
Megumi KuroganePendukung
Rikako AikawaJepang
Yukino HoujouPendukung
Masami SuzukiJepang
Jun ThundersPendukung
Kikuko InoueJepang
Jim SkylarkPendukung
Shinichirou MikiJepang
Misao SakimoriPendukung
Hiroko KonishiJepang
Sayumi UkiyaPendukung
Chiemi ChibaJepang
Karakter lainnya
- Keiko Ochiai
Miki NagasawaJepang - Jun SandersKikuko InoueJepang
- Fen Feilin / Chinami Watanabe (OVA; Gate Keeper 21)Chinami NishimuraJepang
- Saemi UkiyaChiemi Chiba
- Assistant Commander
Fumihiko Tachiki - Devil count [Both TV & OVA]
Hidekatsu Shibata - Mami Ryuukawa
Houko Kuwashima - Matsuda / Tetsuo Ikusawa
Hiroshi Naka - Masao SakimoriHiroko Konishi
- Yasutaka Fukuoka
Kaneto Shiozawa - Francine Aryumage
Junko Iwao - Teacher
Jin Yamanoi - Tokiwatari Tetsuya (Shirei)
Kinryuu Arimoto - Youko Ono
Rei Sakuma - Itou (Ep 15)
Norio Wakamoto - Machine General [Both TV & OVA: Gate Keeper 21]
Shozo Iizuka - Jum Skylark
Shin-ichiro Miki - Satoko Takanashi
Sawa Ishige - Ayako Isagai
Yuuko Sasamoto - Girl C [Ep 21]
Yuka Nishiguchi - Kazuko Ukiya
Yuriko Hishimi - Female Student A (OVA Ep 01: Gate Keeper 21]
Hiromi Konno - Female Student B (OVA Ep 01: Gate Keeper 21]Kayo Deguchi
- Miu Manadura [OVA: Gate Keeper 21]
Yukiko Hanioka - Saemi IkedaYuriko Hishima
- SpecsMelissa CharlesInggris
- Ms. Shimamura, Phone MessageJane AlanInggris
- Narrator
Masaaki YajimaJepang