Kai Chen

"Galaxy Blue!"

Kai Chen is Galaxy Blue of the Galaxy Rangers.

He is also referred to as Blue Galaxy Ranger or Lost Galaxy Blue Ranger - variations on his in-show label, though the latter is more in reference to the show than a proper label.

History
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.

In Lightspeed Rescue, 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.

Super Megaforce
Kai and the other Galaxy Rangers returned as part of the army of Legendary Rangers that helped the Mega Rangers defeat the Armada once and for all, fighting in a huge battle against hundreds of X Borgs and dozens of Bruisers.

Ranger Key
The Galaxy Blue Ranger Key is Kai's personal ranger key. This key along with the majority of the Core Ranger Keys are seen lining the Command Center's interior walls. This key is mainly used by Noah Carver (Super Megaforce Blue) who uses it to fight as the Galaxy Blue Ranger. The Galaxy Blue Ranger key is one of the five water-element Blue Ranger Keys that are used by Super Megaforce Blue  for his Ultimate Ranger Saber Strike attack, which was used once against Skatana. This attack involved summoning manifestations of the five Rangers to attack the target, with Galaxy Blue being the last to go.
 * When the Super Mega Rangers became the Lost Galaxy Rangers while fighting Matacore.
 * When the Super Mega Rangers became the Lost Galaxy Rangers while fighting Gorgax.