Well sherry is the "straight man" of the group.
So part of her personality/character is being "normal" and that don´t stick out as much as the others.
Everyone else in his party is pretty strange in their own ways, including the MC.
Sure she does have some quirks too, but they are nowhere near as extreme as the others.
MC is obssessed with recreating his lost lifestyle ( witch is better then royalty in some regards ) and sex, lots and lots of sex.
Roxxane is a natural born warrior goddess more or less, but the problem is she belives this to be normal as most people she have been around have been too.
This leads to some funny moments when she believes it's perfectly normal to dodge arrows from behind that is shot 5 feet away and stuff like that.
And also to things like the "boobs are useless in fights " as she is the one that focuses most on optimising the fighting potential.
The third slave is for example obsessed with a particular type of food, and she is a expert scout because she got used to looking for "wild growing" mana crystals in the dungeon to support her food obsession.
The list goes some, but im not going to spoil too much of the other characters..... unless you want me too :>
@frankass About why she's a slave (which will be covered soon probably):
Her family ended up in debt and someone had to become a slave to get them all out of the red. She volunteered because she felt she was the least likely to help the family's finances if she remained.