Kai Chen is Galaxy Blue of the Galaxy Rangers and is the team's second in command. He is the deuteragonist of Power Rangers Lost Galaxy.
Straight-laced, sensible, and ambitious, Kai is the classic overachiever. Having been brought up in a strict military family, he always does things by the book and likes everything in its place. His orderly world is turned upside down when he becomes a Power Ranger, and he must learn that sometimes rules are meant to be broken when it comes to saving the universe. He is apparently a good friend of Kendrix Morgan. His fighting style consists of grappling moves and throws, presumably taught by the military.
Kai's strict adherence to the rules initially causes much conflict with Leo, but after an incident in which the Quasar Sabers were stolen, Kai warms up to him considerably.
Kai was responsible for the majority of the meals the Rangers ate aboard Terra Venture. When a lovesick Kai rendered himself bed-ridden for several days after a romantic letdown, the other Rangers complained about the lack of decent food to eat, as Kai was the Galaxy Ranger who either had the greatest cooking expertise, or the only one who was willing to cook for the group.
Kai returned to Earth with the Galaxy Rangers and helped the Lightspeed Rangers defeat Trakeena for the final time. He fought alongside Chad Lee, the Blue Lightspeed Ranger and his Blue Ranger successor.
- Kai is the only Power Rangers character to share a first name with a Sentai character. Specifically, Kai Samezu of Gaoranger and Kai Ozu of Magiranger.
- Fittingly, one of them was also the Blue Ranger of his respective group as well, alongside being water based.
- Kai's serious and ambitious personality contrasts to his Sentai counterpart, Gouki, who is shy and nervous.
- Kai's personality is very similar to Damon's Sentai counterpart, Hayate, who is the second-in-command of the Gingamen.
- Kai is the first Asian-American Blue Ranger, followed by Chad Lee, Lucas Kendall, Blake Bradley, Dax Lo, Theo Martin, Koda, Preston Tien, Ravi Shaw and Ollie Akana.
- Kai is the third Blue Ranger to serve as the team's second-in-command after Rocky DeSantos and T.J. Johnson.
- Kai's personality is also similar to William Riker from Star Trek: The Next Generation and Chakotay from Star Trek: Voyager.