I'd say the fact that's she's a loli with the mind of a grown woman is one of the things that makes her appealing.
Rika: “…Mi-. There is a stranger who is looking at us while mumbling about difficult things.”
Hanyu: “Auauau. …Rika, that person is no stranger.”
Ichirou: “…huh? Whoa!! Oh, I…I’m so sorry!! No, no, I’m not a stranger. Wahahahaha…!”
Rika: “…Yet, his eyes are hooked to my breast and my legs. Nipa~☆”
Ichirou: “No, no, I wasn’t looking in there! Please don’t tell the station officer-!! I was using this mirror to fix my hair…!!”