They don't realize it until Kibum points it out — they've been living under the same roof for six months and if they aren't going out, they can't be anything else.
Kibum says it rather bluntly one Saturday — "Are you two married or what?" Jinki blinks more than the usual number of times he does and Jonghyun raises an eyebrow. They shrug it off until a few hours after, when they're at the dinner table and eating Chinese for the 4th time that week.
"So, are we going out? I mean, everybody says we are," Jonghyun asks, munching on the noodles. "We don't have to be all exclusive, though. I mean, we can be casually dating and still looking for other options."
Jinki nods thoughtfully. "Well then, I guess we are."
Jinki doesn't give it much thought and tucks the idea at the back of his head. When he goes to the bathroom to brush his teeth before going to bed, he realizes that the sole toothbrush near the sink has been a constant in their life as housemates and wonders why Jonghyun never bothered to buy his very own toothbrush.
The next day, Jinki asks Jonghyun out.
Only casually, of course, because anything other than that will be absolutely weird and out of place. "I didn't cook today so we might as well grab breakfast outside. Maybe we can go for a walk after that, then catch a movie and some lunch, then go home?"
"Are you trying to woo me?" Jonghyun asks, caution in the undertone of his voice. "Because I hate taking long walks and watching boring movies."
"Of course I know that." Jinki laughs. He fumbles with his car keys and looks over his shoulder when he says, "Come on, I'm driving. Just get your lazy ass in my car so we can eat." He takes quick steps when he feels a smile tugging at the corners of his lips and thinks, what the actual fuck am I doing.
(They have Subway for breakfast and watch Kung Fu Panda 2. When Jonghyun complains that the movie's too good for his emotional health, Jinki suggests they watch the new Transformers. Jonghyun hits him repeatedly on the arm during the action scenes and leans on his shoulder just a bit when the movie cuts to a new scene and says, almost breathlessly, "That was intense!"
Jinki nods and doesn't say anything, but mumbles when Jonghyun's immersed in the film again, "So were you.")
"So yesterday," Jonghyun begins, then takes a sip of his morning coffee before continuing, "That was really good. We should do it again sometime."
Jinki chuckles. "You should pay this time around. You're unfair; I did all the paying yesterday."
"But you wouldn't let me pay!" Jonghyun shoots an indignant look at Jinki. "Which was weird, by the way. It was almost as if we were on a date and you're my boyfriend and eew." Jonghyun cringes a little. "Just. Eew."
"Eew your ass, Kim. I'm never treating you to Subway again." Jinki frowns. The coffee doesn't taste good today for some reason. Must be because Jonghyun's the one who made it and Jonghyun doesn't know anything about coffee.
"I was kidding, y'know." Jonghyun raises an eyebrow at him. "Can't believe you fell for that."
Jinki doesn't sit well with defeat, so he replies, "Can't believe you fell for that, either."
There's something akin to a realization lighting Jonghyun's features and the next thing Jinki knows, Jonghyun's hitting him on the arm again, each slap harder than the previous. Jinki just laughs because Jonghyun will apologize later, anyway.
That, and Jonghyun's paying for today's lunch and movie. It's a win-win situation.