Ichirou Seii (勢威 一郎 Seii Ichirou) is a commander's aide and a senior pilot.

Personality & CharacterEdit

Seii is a cool customer, under any circumstance, but he is also cautious. He pays close attention to events and people. He is also very brave, as shown in combat. In the mission against the Large Mass Union Ship, he fought without thought to his own life, if it would protect Sidonia and it's people, he would do it.


Since the beginning of the series, Seii is the Commander's Aide to the Captain. He assists in battle and directs personnel. When Gauna 487 was encountered on the mining mission, he was struck numb by his first encounter with a Gauna. In the diagonal acceleration to avoid Gauna 487's attack, he was horrified by the casualty reports, but it would have been thousands of lives or complete anhilation if 487 boarded Sidonia. Soon he leaves his position to Yuhata Midorikawa to become a combat pilot. He participates in many battles, most notably the attack on the Large Mass Union ship. His team almost died off in the attack, which lead to 38 deaths out of the 48 man squad, but over 200 Gauna were killed, and Sidonia was saved.


Seii is a tall man with white hair and blue eyes. He wears the typical crew member uniform until he becomes a Garde pilot, when he exchanges his uniform for a skin suit.

Notes & TriviaEdit

Articles & ReferencesEdit


Knights of Sidonia Characters
Gardes Pilots

Nagate Tanikaze | Izana Shinatose | Shizuka Hoshijiro | Honoka Sisters | Mochikuni Akai | Hinata Momose | Kashiwade Aoki | Izumo Midorikawa | Eiko Yamano - Toutarou Yamano| Samari Ittan | Tonami | Kouichi Tsuruuchi | Ichirou Seii | Norio Kunato | Kaoru Hazama | Ryouhei Kasuga | Kujira Negi | Hamagata | Hashine | Suzuki

Sidonia Command

Yuhata Midorikawa | Ryouko Takahashi | Ichirou Seii | Ochiai Clone

Immortal Ship Committee

Kobayashi | Lala Hiyama | Hiroki Saitou | Yure Shinatose | Ochiai

ET Research Center

Numi Tahiro | Yure Shinatose

Toha Heavy Industries

Sasaki | Shinsuke Tanba | Shijimi

Kunato Developments

Norio Kunato - Mozuku Kunato


Teruru Ichigaya


Tsumugi Shiraui - Kanata

Gauna 487 | Gauna 491 | Gauna 492 | Gauna 493 | Benisuzume | Placental Hoshijiro | Ocarina | Gauna 541 | Large Mass Union Ship | Lem Gauna Wall | Lem VII Gauna | Aulos
Knights of Sidonia
Anime Season 1 | S1 compilation movie | Season 2 | Season 3
Subjects & Topics Sidonia | Gauna | Gardes | Technology of Sidonia | Characters of Sidonia |
Manga Volume 1 | Volume 2 | Volume 3 | Volume 4 | Volume 5 | Volume 6 | Volume 7 | Volume 8 | Volume 9 | Volume 10 | Volume 11 | Volume 12 | Volume 13