Said by others already, but, for Goddess Melfina's sake, at least give the poor little sister proper clothes. You can see her fricking panties when she's running around. That's just wrong. Unless the MC is the kind of special pervert who enjoys looking at his little sister's underwear.
#1. Haha Unique Skill "Cut Marks". Emo girl confirmed. Best keep her away from razor blades.
#2. Bad image of the name "Rio"? Why? Was he raped in Brazil or something?
#3. Sister was a good choice. Careless expansion of the harem will only lead to discontent amongst the existing members... and she is clearly an unappealing skinny stick with no secondary female features, so the sister role is perfect for her.
@Soticoto he has bad memories of the name Rio cuz of how he was exposed by the guildmaster Rio as an other worlder and his personality in general I guess