Yeah, sure, except for the fact he's not a maou anymore. Even a hero with some wits would have done the same. They were, after all, from a world full of war and wickedness, so being cautious should be a given until they figured out what the world is all about. If the dude was still a maou, he wouldn't be frying fries happily. Even if he had ended up at the restaurant, he would have arranged for the joint boss to get into an accident and be conveniently present to take over her place temporarily. That would be something a maou would do - IF he ever bothered to work at a fast food restaurant, which is a big if, especially considering I still believe he didn't know he had to hide from the winning people of his own world. Instead this guy is genuinely happy he got a permanent position as a burger flipper.

If that's the limit of his ambitions, why did he start a grand war to enslave the whole world back in his home dimension?