Nanase representing casual readers trying to keep track of all of this comic's nonsense.

Granted, Kevin was just in the main story, so when this comic was new, it would be hard not to remember Kevin. someone reading this at some point in the future, however, might be on the same page as Nanase.

This isn't definite canon, but Elliot MIGHT be doing a movie review with Susan the day this comic takes place. If a recent review is established in canon sometime soon (in-universe), this was probably the day it was done.

Grace, meanwhile, was probably invited somewhere by her increasingly large social circle. Or she could be somewhere with Ellen. Or at the comic shop. There's actually a lot of places Grace could be, but wherever it is, she's probably with other people doing something.