The stall door opens

At this point, Aoi's entire body was pressed against the door just so she could hear Chihiro better.

The pressure that Aoi was putting on the door's lock eventually became too much as it snapped, making the door open and making Aoi fall forward to Chihiro's feet.

Aoi looked up to see Chihiro still masturbating, so caught up in the feeling that they didn't even realise what had happened, his pleasure was dominating every sense he had.

From Aoi's perspective, all she could see was Chihiro hands reaching down to his crotch that was being obscured by the toilet seat.

She just kept watching, too embarrassed to say a word.

"Aoi... AOI, AHHH!" Chihiro continued to moan out her name in an increasingly louder tone as he finally finished.

Chihiro went from intensely touching himself to a daze where he relaxed, not giving any care in the world about anything.

Soon enough he started to come back to reality, he finally noticed the tanned girl lay at his feet looking up at him.

"AOI!" Chihiro finally realised what he had done. He stood up with his hands covering his crotch, hoping that Aoi didn't see everything.