So, after taking a peak at the opening of the manga I'm kind of shocked at how they adapted it. Rather than taking the normal option of following the manga closely or inventing something out of thin air they opted for a third option: take various scenes from the manga but randomly swap characters out and replace them with other characters meaning that the scenes no longer make sense. What?
They combined the first two chapters into a single story so they fit into one episode. Since we knew they were going to rush the beginning that was probably the only way for them to do it and they didn't do a bad job.