The main motivation for MC is weird.
The only things he want is to save his mom from impending doom of invasion.
Yet I think he can already save his mom in various way
1. Adventurer way
He had 4m yen and a rank-E adventure. Therefore he could go somewhere else??? Somewhere where the war doesnt happen, or go into the neighbour country as told
2.Alchemy Way
He literally can spend his time to improve the plane design and make it have 2 seat to bring his mother ANYWHERE he wants. Or He can literally create house in the wild(or at least Build it easier) with this cheat skill
3.Concealment and appraisal way
He can steal(Evil path) or hustle using appraisal to have money to go anywhere even if he are not a rank-E adventure
Literally there is no need to save the villainnes.
I guess the previous comments was right,the author submit this manga as "Isekai-I love the villain" Trope in disguise while drawing whatever he's like.