Taiha got to the bunker, which was a little distance away from where they set up the shoot.
He stood in front of the door and yes, he could hear muffled moans. If it had been anyone else who came to call them then their secret would've been exposed.
He was tired of them using every outing site as their makeout location.
This wasn't the first time something like this was happening.
When they went out for a night shoot where the twins were apparently supposed to be dressed as flamingos, he saw one of the decs had fallen off of one of their costumes and went to return it to them by himself, since everyone was busy doing one thing or the order.
And in the part that was set up for dressing and changing outfits, he heard them making out. They weren't even worried that someone would walk up on them and discover their little secret.