Ema

"Are you all right? Would you like big sister here to explain it for you?"

An "adult" older sister-type girl, a bit of the meddlesome type. (To put it simply, a loli with big boobs.)

Her height gets pointed out often, but she's very feminine and is very capable of taking care of other people, so she does feel like an "adult" older sister. She also has a more maidenly, romantic side to her, but is still that "adult" older sister.

Be wary that she will get mad whenever you mention her height, or treat her like a kid. But the way she gets mad is also really cute, so sometimes you end up wanting to point it out just so see her expression.