Kiriko was Seina's childhood best friend and basically his personal nurse, constantly patching him up after whatever disaster his bad luck caused that day. She was fiercely protective of him, and her younger brother Kai would help rebuild (or just build from scratch) whatever bicycle or vehicle Seina had destroyed. The two of them made a pretty solid support system.
What nobody knew—not even Kai until much later—was that Kiriko actually had royal blood. She's distantly connected to the Jurai royal family, which comes with the added weird detail that she's 33 but looks like she's in her early twenties. She spent some time as one of Seto Kamiki Jurai's ladies-in-waiting because of this connection, which eventually got her a cushy job in the Galaxy Police's immigration department.
That job was how she found out Seina had enlisted in the G.P., and she immediately tried (unsuccessfully) to talk him out of it. When she got reassigned to the Academy to work alongside Amane Kaunaq, she basically moved in to the same house just to keep Amane from making a move on Seina. Fair motivation, honestly.
Eventually though, Kiriko started feeling outclassed by the other women around Seina—Amane, Ryoko Balta, Neju Na Melmas. Everything changed when she bonded with a second-generation Jurai tree called Miyuki during a ceremony. She became Kiriko Masaki Jurai, and Miyuki helped power the Kamidake II alongside Seina and Amane's ship.
Like the other women in Seina's life, Kiriko ended up in a political marriage with him. They all witnessed the same bizarre incident where Seina got kidnapped and seduced by what turned out to be Rezma Union diplomats asking for Jurai's help. Now she, Amane, Ryoko, Neju, and the Rezmans are all married to him and serving together on the Kamidake II—probably the only Galaxy Police crew where everyone's married to the captain.
As a G.P. officer, Kiriko has serious training and access to their weapons arsenal, plus natural Jurai strength. She once used a cloaking bodysuit in combat to get the drop on enemies, and she's known for getting completely tunnel-visioned during fights. One time she walked up to an opponent covered in blood from previous battles and only then noticed Seina had been watching the whole thing.
Content compiled by AnimeList.moe from publicly available sources.
