Why does he need to leave it with anyone? It's not like being left alone it will suddenly revert into some trash yukkuri break everything state. Get her some toys, she was playing with a ball before the whole incident started.
Actually, I think it's concern. Mister may not know how long he has to leave, so he might worry that the Reimu might run out of food if he has to leave for weeks.
Am I anywhere near correct in assuming (just based on the images) she's avoided sharing her experiences with him so as not to drive a wedge between him and his friend? Jeez. Yuudoro seems to have a real thing for making blameless yukkuris suffer. Not that I'm complaining. I'm sure it gets exactly the response(s) he's angling for.
*Update* Top to bottom, right to left. From now on I'll put the parts in Japanese quotes in [square brackets], comments in (( double brackets )) and sound effects in *asterisks*
"Yu'... Reimu tri..." *hu* ((or *ding* like a light bulb))
"Why did you leave her alone when she tripped! Not taking it easy"
"I rolled around in mister moving house!" *Yuhe'* "I was so happy easy I hit myself!"
[ "Hahaha. Clumsy." ] *pet* *pet* "Yu-..." "I love Mi-ster I can really take it easy"
"Yu?" [ "And so, I actually have more work to take care of, so I have to go back tomorrow. ] [ "Can you stay at his place for a few days again?" ]
Nah, it's his own yukkuri. You're allowed to do whatever the hell you want to them. And a yukkuri life isn't worth a human, anyway (even if people are terrible).
And besides, it's not like the abuse here was pointless. I didn't like this series at first either, but the translations reveal that anon's a breeder and owner of the petshop, and he was mindscrewing and abusing it to break down the other yukkuris and set an example of what can be done to them. Thus making them into extremely loyal yukkuris because they're terrified of doing anything that can lead to abuse. Quite a clever way of making well-behaved pets, actually.