My Life is an Isekai, I think

Katsuo is routine oriented and in his second year of high school, when something weird happens. He wakes up, and going through his usual routine, he starts noticing some small differences, and others that are quite large.
Is it a prank?
T.V. show?
Amnesia?
...Isekai??

I do write a little as a hobby, but this is my first web novel. So bare with me!
Critiques welcomed and maybe even encouraged.