This is a flashback scene showing Young Hachemi (10) and Young Farfat (10) on the rooftop with their pants down and they are playing with themselves (hidden by their hands).
The boy (Park Dae-Su) checks his penis worrying about the castration. Then the girls caught him and laugh at it. Dae-Su runs away, but his rear is exposed. He continues checking his penis, and the girl Seong Song-yeon (played by Lee Han-na) finds him. She gives headwear to Dae-Su, covering her eyes.
A boy (you cannot see his head but he is in Addi’s bedroom) is shown standing naked in front of a full-length mirror during a dream. Shadows and light flare effects mask his nudity.
After ballet class, Lara locks herself in the bathroom and removes the tape the holds her penis down while looking at herself in the bathroom mirror. The actor, Victor Polster, is shown naked apart from the tape.