@cool-sunglasses Aoyama isn't really manipulating him, she so far has been the only one to be nice to him without plotting something to make sure he doesn't leave her, she just happens to also be batshit insane and wants to take out any competition that could get in her way.
Maybe it's not even the mom that's calling him, maybe it's Fukishi or his dad. If it were his mom I doubt Oshimi would pass on the opportunity of dropping a "Sei honey" for maximum horror.