To those that are wondering, first skill x2 abilities multiplier(atk,def,spd,eva,etc.) then the 2nd one when defending property another x2, for total x4 for now.
@yeetmaster6981 The LN gives more info, but long story short, it's similar to what other isekai manga do with taxes. Instead of charging a huge fee to open a store, they just have a percentage based tax on the merchants' profits.
As a reader of the LN, the final scene was much cuter, with puffed cheeks complaining about "that oda nobunaga job". Also, any missing logic for weapons and other things that should make sense, blame the artist haha.