Poppo really fail to save Menma as she was drowning?
In real life, I doubt he would have just run away for help. It is known that her body washed away so if he saw her where she fell initially, it must have been just as she started drowning.
Is it known that he saw her, in the middle of drowning, and just left? Or did he see a body, or maybe just the flip-flop?
I need to know...