Acura Akari

Japanese name:

アカリ・アキュラ

Toru's sister who's unrelated to him by blood. She respects and is fond of her brother to such a degree that she gets angry at whoever speaks bad of him, even if that person is himself. Her rather bizarre levels of stupidity and radical degrees of respect for her brother can cause her to comically proclaim contradicting claims, although she admits and is perfectly fine with being an idiot. She isalso able to use the Iron-Blood Transformation, however her markings do not crisscross like her brother's and are much thinner. Her weapon is a sledgehammer with a retractable handle and a spike on one side of the head. Akari does not hide the fact that she is in love with Toru and is jealous of any other girl who gets close to him.

Wikipedia