I know it's the norm to do introduction posts but it'll take forever and people usually lose interest. I also don't think it's necessary for characterisation. 

Just my opinion - we should start on a typical school day, they know they have powers and they know they're going to be involved in some sort of event but they don't know if anyone else is involved. We roleplay the day, maybe bump into each other and write about their relationship dynamics. Then the Unfair Monster arrives and they're all surprised to see each other. 

If you think about it, our characters aren't gonna have a chance to really develop and get to know each other until after the first monster because they need it to tie them together. Option 2 means we get to developing faster.