I didn't really like the bug effects in the beginning, I feel like you could have added more (like color distorsions, blur etc) to make it look more realistic.
And about the white stripes/grid overlays, it's maybe a bit too repetitive (and the grid could have been more discrete).
Some of your rotoscopies look a bit weird to me because of the movement of the scenes. Like for example at 1:12 when Saber "arrives" it's a very static scene, while just before there was some kind of horizontal movement. Same at 1.43 when "spiky-haired-guy-whose-name-I-can't-remember" leaves: the next scene should follow the same movement. And finally, I think some scenes in the last chorus where a bit too static.
But actually all of these didn't bother me that much
. I think the cross-over was a nice idea and it worked very well. Overally I really enjoyed your vid, so nice job! and good luck for the contest
PS: 1:22/1:56 is the same scene