Honestly, I dont see what the big deal with Mio is, I mean, she is an annoying little fraidy cat, and not in a cute way. She is afraid of too many things, and reacts way too severe a way for it to be cute, as it seems more like she has serious issues.
Personality wise Mio isn't the big deal (I find her annoying most of the times). Physically she has some cute points but that's not enough for me to like a char.
However, in the legs and feet section, she's highly ranked in my book. Still beaten by (mah) Tsumugi <3
personality wise, all the characters are just common arc-types. Mugi is the Mi-Lady with no knowledge of the "Common world". Yui is the the lackluster main character with a heart of gold, Mio is the fanservice and Ritsu is obligatory "Man" girl where you get only 1 episode(Or chapter in manga) where they might act a little girly, then its back to being a man again.
Oh but Ritsu is the "Man". Every Girl harem always has to have a "Man" character. That doesnt necessarily mean Tomboy. On the contrary, Ritsu is still very girly when you compare her to the usual "Boy" girls that are almost always depicted as tomboys. Like using "Boku" and wearing shorts and pants all the time.
