
Okay I thought the uke will make move first but the seme said "hold my beer im stepping up first"
But can anyone explain to me who this uke really is and why he suddenly want to work here

No he wanted to take their money and run. Being a bookkeeper means keeping track of the profits, losses, costs, taxes, ect. That the company generates. Back in the day all of that was kept in books, hence “bookkeeper” “bookkeeping.” Back in the day people would manipulate the books so they wouldn’t need to pay as much in taxes or in this case they could move money without people knowing. It’s a form of many different types of fraud.

I think the grandpa also went through the same situation so he's trying to find a way so the two of them did not suffer the same.
He probably try to separate them at first, hence making Gensukei the apprentice for the uncle's character but I guess he realized that there's no way to separate the two so he try to find a solution
It has beautiful message
Screw fate...you can defy it. Just follow what makes you happy