TSF story about a pair of step brothers. One of them is Hayato, your normal, average guy, while the other one is a crazy yandere obsessively in love with Hayato who started dressing as a girl because Hayato once jokingly said that he wanted a little sister. Oh, and also he just acquired a magical collar that can turn anyone (mentally) into a loyal female dog.
*All characters depicted in this work of fiction are adults, regardless of their visual representation or textual description, and are not based on any real person*