Komorie Nanaru

Sousuke's "current" younger (step)sister whom he's been with since childhood.

Nanaru is in her first year in high school. She's cheerful, but innocent too, and she's a free-wheeler. She's pretty silly and weird at times, which you could probably guess from a girl who considers her raison d'etere to be cracking jokes. The vast majority of her brain storage space is used up on jokes and puns.

She has a fondness for teasing, which amplifies tenfold when her brother is the target. But that's not to say she doesn't also love having him dote on her.