And I can't understand what Shuu is trying to say in his last bubble.
Can anyone help me out?

Sigfried666 said:

And I can't understand what Shuu is trying to say in his last bubble.
Can anyone help me out?

Probably a conjunction of まぶしい and 過ぎ、so something like "so bright!/so brilliant!/so sparkling!" I guess?

Sigfried666 said:

And I can't understand what Shuu is trying to say in his last bubble.
Can anyone help me out?

Evilplates said:

Probably a conjunction of まぶしい and 過ぎ、so something like "so bright!/so brilliant!/so sparkling!" I guess?

マブい（眩い） concatenated with すぎる（過ぎる）.

マブい is used to describe someone (female, usually) with a face beautiful enough to turn heads. It's kinda antiquated slang, from the eighties.