You decided to put it back to where you took and just ask your girlfriend later about the costume later.
You go to the living room and decided to watch some TV to pass the time while you wait for your girlfriend to come home from work, you took some snacks on the fridge and lay down on the couch as you watch your favourite shows.
After a few of hours, your girlfriend came home, she puts her bags on the sofa and slumped on the couch.
"Work was exhausting, but at least I can energize thanks to you." She says as she snuggles next to you.
"So what are you watching?" She looks at the TV. "Just my favourite show, so.. how was work?" You ask.
"Let's not talk about that, for now, I just want to be with you, right here on the couch." She hugs you as she lays there with you.
"Okay then.. Oh actually I have something to tell you." She looks at you. "Oh, what is it babe?"
"Well, I've been cleaning the house and doing the chores.. and while cleaning, I found a mermaid costume on your closet, I was curious so I took it out and decided to see it and feel it's material, and for some reason, I couldn't stop imagining you wearing that and be a mermaid for me, it's.. kinda hot to be honest.. So now I want to ask you something.. Why did you buy it? I'm curious, do you want to be a mermaid performer?" You ask her.
"Well, not really, I just bought it because I want to try out the costume, nothing really much, unless you want me to be a mermaid performer, hah, just kidding, I earn more at my current job." She giggles, then she looks at you again.
"And actually, I didn't buy just one mermaid costume.."
"Oh? Did you buy for someone else?"
"It's for you hahaha, not really a mermaid costume if it's for you, more like a merman costume, wait I'm going to take both of it.." She walks to the bedroom and came out with her mermaid costume and your own merman costume.
"You bought one for me? Wow, that's actually cool." You said happily.
"Well I don't want to be a lonely mermaid without her merman right?" She giggled.
"Anyway, I'm in a mood for one of us to try the costumes, what do you think?" She asked.
"Hmmm.. I think.."