Little Sister

Biography
The Little Sister is a grade schooler living in the Town with both parents and her Oniichan. She acts like a grownup to impress other people but especially for her brother. She loves to be coddle by her Oniichan even if she doesn't always wants to admit it.

Personality
A precocious child she tends to act a like a know-it-all to impress grownups. However, she's still a child and becomes extremely jealous just thinking of her Oniichan spending time with anyone else.

Episode 41: Detective Interrogation
While at her cousin's workplace, the police station, she begins to talk with the Butler. She stays here whenever her Oniichan is out late at his baseball practice.

Episode 23: Little Sister Can't Sleep
During a thunderstorm she sneaks into her brother's room and ask to sleep next to him. She reminds him that he promised he'll never get a girlfriend. It doesn't make sense to have a girlfriend when all he already has her.

Episode 11: Sick Little Sister Roleplay
She's been sick lately but that doesn't stop her from confronting her Oniichan. Especially after she hears he has a girlfriend behind her back. When he doesn't agree she starts to get really really angry.

Episode 38: Clingy Little Sister Helps You Sleep
After taking back her Oniichan from that stupid girl she decides to let him sleep. After he's settled in she decides to finish up with the girl in the basement.

Episode 45: Yandere Little Sister's Interrogation
She decides to have a very serious talk with her brother's girlfriend. Already tied down to a chair the girlfriend is unable to resist. With a pair of scissors the Little Sister begins both the interrogation and haircut. After making it very clear that Oniichan belongs to her the episode ends...

Oniichan
She loves him to the point of obsession; even making him promise never to get a girlfriend. However she eventually decides to forgive him and takes him back.

Cellphone Girlfriend
Her worst fear and the person she hates the most for stealing her Oniichan.

The Detective
They're cousins...that;s it.

Trivia
Reminds me of Yumemi Takanashi from Yandere No Onna No Ko Drama CD 2. Both share a love of their "oniichan" and can't take it when he decides to meet with other girls. When they realize there's competition both use a pair of scissors to reclaim their "o-ni-chan".