I think his grandfather does mourn Mei, but I'm not sure for that.
I'm fairly sure a lot of people mourn her still, as she seemed to be some sort of fantastic person, I have a few hunches where this will go, but I'm not sharing.
All I can say at this point is that the first half of the show will blow the minds of ours away, and the second will just fuck us hard, that is, if my hunch is correct. Which rarely is wrong

The fact however remains that time seemed to pass rather fast while watching the first episode, I thought that it passed in around 10-15 mins and it was full 25 mins, that alone says how interesting it was.
That or Prof. Fornsworth messed with chromatons again (Futurama).