How is this girl so smart even though she does not school and is malnourished?
Internet is a big school, you know, you can learn everything on internet.
The plot demands it.
Yes, it's stupid. Yes, the later novels fix this problem by giving them rivals who are equally as Gary Stu and Mary Sue as they are.
This world needs more wispy voiced lolis.
How is it stupid for someone to be smart without going to formal education? Some of the world's greatest minds are failures and drop-outs.
eh, the male MC is less of a Gary Stu and more of a Magnificent Bastard and Chessmaster
he makes very few mistakes and that can get annoying but his extreme separation anxiety from his sister can be considered a critical flaw on his character so he's not perfect
Except proper social interaction.