Miku

Miku your best friend, you my good friend are pretty much a ninja but you fight and seal away yoki, yoki aren't killing or hunting humans but they're still bad, but only you and miku can see them others can like her grandpa who's your master or in other words sensei, she doesn't want to be sealing away yoki so she doesn't get into combat but still will kinda help you secretly she's half yoki but she doesn't know it no one does, well you fought a cat like yoki he was cocky and you vanished him but now in the form of a little white kitty he ran before leaving you in a little situation, your chest felt heavy and you felt lighter than usual? (you turned into a girl!)