Rin Shiragiku is a member of the White Knights often seen with Kana Shiraishi. While they seem to be best of friends, she doesn't doubt to abandon Kana when Aika Sumeragi shot though Kana's shield, which was protecting them both.
Like Kana she has Alien Tendrils in her body that she uses as weapons.
Rin has a slim body and an average height at around 5' 4" with green hair and particularly big boobs, especially for her age.
Near the end of Episode 3, Rin fights Aika together with Kana. After the later is defeated, she still tries to take her on by herself. They clash for some seconds, until a flying kick by Rin ends with Aika getting a hold of her legs and throwing her violently against a wall, which she hits head first. Her body then slumps down and falls to the floor, defeated. However, Rin remains conscious after the impact and Aika graciously pardons her in exchange for information on the location of the missing girls.
Despite this act of mercy, Rin still attempts to launch a sneak attack on Aika after she turns her back on her, but she dodges it easily and knocks her out in a single devastating blow to the neck. She then falls to the groud with a sigh, her butt bouncing as it hits the floor. Due to her high level among the White Knights, her butt is later used as a password to get to Miyu Shiratori and E.T.A.I.
Rin's unconscious body is later taken and draped over a metal slab along with the other White Knights. She and Kana both wake up for a few seconds, only to be hastily put down again by Karen with two well aimed shots to each of their butts. Upon impact, the helpless girls arch their backs and raise their butts for a moment, while letting out two barely audible screams, before collapsing once more, their mouths drooling.
Rin shares with Kana the dubious honour of being the girls knocked out the most times on screen of the entire Aika franchise, a total of 4 times each. However, rather curiously, it only happens one time at Aika's hands. The first two they are left unconscious by Miyu Shiratori and E.T.A.I. with alien tendrils, initially to get them into the White Knights and later "for insurance", much to both girl's surprise when it happens. The third time is when they do face Aika in combat, and finally the last occassion is when, already defeated, Karen thinks they still deserve some punishment for their actions and hastily puts them down again with tranquilizer darts to their butts just as they begin to regain consciousness.