Kuesu is a daughter of another demon-slaying family, who seek to ally themselves with the Amakawa family through marriage. She appears to be part of Yuuto's past and claims that Yuuto's grandfather had promised their marriage. She is highly aggressive and assertive, going so far as to kiss Yuuto twice in front of Himari just to stake her claim. Unlike Yuuto, she is trained in her heritage, and is fully capable of fighting. The Jinguuji family is seen by the ten other families as heretics for using Western magic. Her magical powers are rumored to be as powerful as that of ten people.

(Source: Wikipedia)