| Name: | Niji Sei |
| Meaning: | Rainbow Star |
| Mother: | Lady Irina Sei (Sailor Iris) |
| Father: | Irina never said |
| Birthdate: | August 20 (Leo) |
Physical Description:
| Hair Color: | Light blonde |
| Eye Color: | Opal (colorful) |
| Hairstyle: | He has bangs and his hair is short. |
| Kamen Suit: | Golden shirt and pants. White mask and collar. His cape is of the rainbow colors. |
| Best Friend: | Akuji Kai, Ryuu Gingekko (his adoptive brother) |
| Love Interest: | Umi Gingekko |
| Favorite Food: | Ice-Cream |
| Strenghts: | Getting in trouble |
| Likes: | Making fun of Ryuu and Nintai |
| Weakness: | Revealing his true feelings |
| Dislikes: | Ryuu's lectures |
Niji was raised by Megumi (Sailor Andromeda) and her husband dafter his mother left to the Universal Palace. He and Akuji are best friends since they know each other and along with Ken and Kage always hang together. He is a playboy, but has developed strong feeling for his adoptive sisters Umi. Only Akuji knows about it.
| Weapon 1: | Rainbow Sword, sent by his mother |
| Attack 1: | Blinding Kristall Rainbow! First attack. |
| Attack 2: | Rainbow Razor! Power-up once he got the Sword |