Learned the meaning of the final sentence

I posted on japanese.stackexchange.com asking for help understanding that sentence I couldn't translate and received a great response from a user named Chocolate who broke it down piece-by-piece. That sentence means "Why? ... I can't tell that to Mom.", so the first page says "Sachan ate breakfast urgently. Mom always says 'please ate slowly' but today it cannot be helped. Why? ... I can't tell that to Mom." Now that page one is done, I suppose it's time to move on to page two!