Ariana Grande and Mac Miller have been pretty public about their newfound relationship. While some cynics may have labeled their PDA romance as an elaborate publicity stunt for Miller's Grande-featuring new single "My Favorite Part," the rapper insists their relationship is legitimate and came about naturally.

Miller contacted Grande about working together again -- the pair first collaborated on Grande's 2013 track "The Way" -- on his current single "My Favorite Part," and things quickly evolved from there.

"I wrote that love song before I saw her. We're very good friends first and foremost," Miller told PEOPLE about the track. "We made that song and started becoming close again. It's very dope and I like how that worked out."

Miller continued, saying his time spent in the studio with Grande only solidified their connection.

"It was great. There was no awkwardness or weirdness, it was how it always was," he said. "Just both of us older, more mature and more sure of ourselves. When we first recorded together we were young and figuring it out, which we still are, but now seeing her growth and my growth – it's great."

"We hung out for a long time and everything just happened organically," the rapper continued. "We love making music together – we do that always. But she's my best friend in the world."

Miller also commented on the couple's live performances, saying their comfort with one another is evident in their onstage chemistry.

"We've performed together a lot – when "The Way" came out, we did all the shows," he said. "We're both relaxed – we just have fun. And everybody gets an 'awww' moment."

"She's just very warm and comforting," he continued, unable to stop gushing about Grande. "She's very caring but, also, we have a lot of fun. We go on adventures. Adventures can be driving around in the car aimlessly. It's great to be able to do nothing and be doing so much."

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