鍵ノ寺千歳

Apparently, Tsukasa saved her from falling off a cliff when they were children. Chitose wants to use her own life for the sake of Tsukasa to pay her back. She obviously doesn't want Tsukasa falling into Nasa's hands. She has two maids: Aurora and Charlotte. Chitose has a personality that quickly bends from being strong to whining. She considers Tsukasa her sister.

(Source: Tonikaku Kawaii Wikia)