An escape room!

"Oh, I know, how do you all feel about escape rooms?" Setsuna finally asked them.

"Escape rooms?" Ochaco asked, blinking.

"Yep, they're rooms you pay to get locked in, and you have to solve puzzles to get the key to get out! It's a game of wits!" Setsuna nodded. "And I do so enjoy games that test my mental chops!"

"...that actually sounds pretty fun to me," Izuku nodded, grinning at the thought.

"Of course you'd think so, Izuku," Momo smiled fondly. "You like overanalyzing things."

"True, but you also like testing your mind a bit too," Izuku noted, and Momo had to agree with that.

"Hmm, it's not exactly my personal cup of tea, but why not?" Ochaco asked, willing to go along with it, perfectly okay with doing activities others preferred just for the sake of spending time with her Master, girlfriend/sister slave, and potential future girlfriend.

"Cool, there should be one over that way!" Setsuna grinned, and they immediately proceeded to start making their way over to the building she pointed at. Izuku caught himself staring at her ass in her jeans a few times.

"This should be fun for you, Master," Momo whispered in Izuku's ear, once again doing her routine of hugging one of his arms with her own. "Being stuck alone in a room with three lovely girls? Whatever will you do with this? Even if you don't incorporate Setsuna into the harem right now, I may have an idea or two..."

Izuku gulped, looking at Momo, then at Setsuna as they walked, thinking over whether to humor Momo's idea or not.