" Isn't that a shame ? I've got a lot more power than 'quite a bit' "
- Tail Blue (テイルブルー? Teiru Burū) / Aika Tsube (津辺 愛香? Tsube Aika)
- Both TailBlue and Aika voiced by: Yūka Aisaka
- (Japanese); Sarah Wiedenheft (English)
- One of the heroines of the Twin Tails, Aika is a 15-year-old freshman of Yōgetsu Private Academy, ( and childhood friend of Soji ), and when she does her Henshin, she becomes the Twin Tail Warrior TailBlue. TailBlue has a complex dysphoria with her body, especially with her flat, underdeveloped chest. As TailBlue, several Elemelians take turns mocking her almost flat boobs, shown off so well by her tight-fitting Tail Gear outfit. She has a violent attitude toward Twoearle, who often teases her about her small, childlike chest. When she first became a Twin Tail Warrior, she is mostly ignored by the populous, until later when Tail Yellow joins the team. Before TailYellow is commissioned, TailBlue begs Twoearle to allow her to 'trade in' her blue Tail Gear for the upgraded and more powerful yellow Tail Gear, but she finds that her 'spiritual attributes' are not compatible with the yellow gear, so she redoubles her efforts to command the blue Tail Gear to optimal performance.
- Unlike the other two Twin Tail Warriors, when Aika transforms, she stays approximately same age as she is in real life. And unlike TailRed, who changes gender from male to female, TailBlue does not change gender when she powers up, but remains a teenage girl. In battle, Aika has an outstanding ability for fighting, as she was raised by her grandfather with martial arts skills. As such, she is actually the most powerful of the Twin Tail Warriors, outranking TailRed and TailYellow in sheer strength. TailBlue also comes to have almost absolute fearlessness in battle, willing to take on the most powerful of the Elemelians with no more effort that if she were asked to take a garbage can out to the street. She is known by her blue Tail Gear when she transforms, and her weapon is Spear of Water, and Wave Lance (水の槍ウェイブランス? Mizu no Yari Weibu Ransu). She also uses Execute Wave, and shares Brake Release with TailRed.
- In Vol 8, she gains the upgrade of Eternal Chain.