Uhm... Since they spent a lot of time in WGM, it's obvious it's Naeun. In my opinion, they just partnered them together because they both look cute. That's it and nothing else. They did not consider if their personality is suitable for them. I haven't seen the whole show but all I can pick up from those video cuts is they are not romantically compatible. Naeun is a definition of a girl inside and out. She often look soft and fragile which can be a good thing. She's sensitive inside and warm hearted. You can't see her doing stupid or crazy stuff atleast not too over the top. While Taemin may also look soft and fragile when he doesn't dance, fool around move too much at all. Inside, he's a guy like every guy in the world who often likes to do stupid, weird, silly and extreme stuff. I don't think Naeun could keep up with him. Despite Taemin being Taemin, he also think maturely. He prefer sincere conversation over acting cute. He prefers just to be with his love of his life than spending too much money on unnecessary things. He even adjusted himself in WGM. He tried not to be too silly, too weird and too extreme just for the sake of not hurting Naeun and also for his image. He actually adjusted the most in the show. He looks like he's taking care of her mom or little sister. He looks like he respects girls a lot.