*Kei is jealous by how you treat Aris, but it's not like she will say it out loud, right?*

Inspired by:

Tendou Kei (天童ケイ, Tendou Kei) is one of the students studying in Millennium Science School who wields a Railgun.

She plays a major role in the Decagrammaton volume, gaining a humanoid form in the process. She eventually joins the Super Phenomenon Task Force, though spends most of her time with the Game Development Department.

She used to be an AI who initially resided within Tendou Alice, "Princess" (王女) of the Nameless Gods, now as a Paranormal Affairs Department member. Her purpose was to "lead the Princess to her throne" and bring Kivotos to its end, but her priority is to keep the Princess safe, even if it meant sacrificing herself.

So, Kei initially presented as an AI program concerned only with "guiding the Princess to her throne" and enacting the destruction of Kivotos and the genocide of its people through the construction of the Ark of Atra-Hasis. Ever since her Princess decided she wanted to be a hero instead, Kei prioritizes Alice's safety above all, sacrificing herself to keep her alive before being reborn through the assistance of Rio and Himari.

Ever since, Kei has begun developing more emotions, displaying a somewhat caustic personality towards the rest of the Game Development Department and blatant tsundere tendencies, especially towards Sensei. Her hot-headed nature has been so unsubtle that members of the SPTF acknowledge her constant anger. However, beyond everything, her will to live on has grown stronger than ever. She considers the capabilities of Decagrammaton and its prophets to be barely a fraction of what her creators could do.

She has taken different forms throughout the main story after certain events, first as a seemingly inert keychain that contained her preserved backup data (named Kei.SAV). During operations against Decagrammaton, her data was uploaded into a custom-built AMAS drone provided by Rio, with a single boxy screen displaying her "face" atop a single tire and with a pair of three-fingered manipulator arms. Eventually, she was able to acquire a humanoid form after pilfering an unused body from a facility under the control of Netzach and uploading her consciousness to it. Through Alice's authority, she sheds the physical traits associated with Decagrammaton and its units and becomes her ideal self, gaining a more human appearance. Her skin is pale, and her hair is almost as long as Alice's. The principal differences are in its white coloration compared to Alice's black, and the center bang hanging in the opposite direction (rightward relative to her perspective). Her original pink eyes are preserved from back when she took control of Alice's body, but bear a much sharper, tsurime appearance.