Yui (優衣) is a member of White Knights. She was the part of White Knights Squad No. 1.
Yui has short, dark brown hair. She is seen in her White Knights uniform and black high heeled shoes. She appears to be the tallest of the trio
Yui is one of three most recent White Knight recruits. Their duties are to guard the church which covers the entrance to E.T.A.I.'s underground lair and helping Miyu capture more girls to increase their numbers. Like all White Knights, their combat abilities are of a level that can rival trained combatants like Aika or Risako.
She is first seen at the beginning of episode 1 inspecting a red haired girl who is later knocked unconscious by the Alien Tendrils and Yui hoists her over her shoulder for a final inspection which the girl passes.
She fights Aika with Misaki after Nanami is defeated, but is knocked out by an unseen blow after Aika decides to get serious. Though the details are unknown, we do hear her many desperate screams as Aika makes quick job of her. She is then shown falling to her knees, with her chest subsequently dropping to the ground and her panty-clad buttocks in the air.
When we next see her, Karen has moved her body and she is now lying flat on the floor, face down and legs spread. Her skirt rests over her butt, but it is so short it barely manages to cover it. Not happy with this, Karen hikes the skirt all the way up to the waist, to leave the ass fully exposed for proper examination. She explains to Aika how all the White Knights have a strange star shaped mark on their buts.
Later, she, Misaki and Nanami are picked up by three other White Knights Yui is later seen slumped over Reiko's shoulder, Miyu and E.T.A.I are there , and they are angry at the trio's failure so they decide to demote them and put them with the other girls they have captured
In the beginning of episode 1 the girl Yui hoists over her shoulder has Red hair and at the end of the episode another girl with Red hair (Reiko) hoists Yui over her shoulder.
Nanami and Misaki carried their captives and were carried over the left shoulder, Yui carried her recruit and was carried by Reiko over the right shoulder