For a comedy series?
The best combination.
They have to fit in and lay low until they figure out how to recharge their magic. Something they have again hilariously failed at. Taking over the yakuza wouldn't be very effective at the laying low part. Emilia probably would have figured it out sooner. The fast food employee situation nearly threw her off completely.
Nevertheless, he's decided to have his store conquer the rest of the franchise first and get more money. You gotta start somewhere.