The Biebs joined his pal onstage at The Forum in Inglewood, Calif., where he first accompanied her for a performance of "Love Me Harder" (he sang The Weeknd's lines).
As you can see in Just Jared's concert footage, Justin and Ariana got a little flirty with their dance moves. And while the Biebs didn't get too grabby, it seems he was still too handsy for Ariana's boyfriend Big Sean. The rapper reportedly tweeted (and quickly deleted),"This kid is about to learn not to touch my girl like that. Beliebe that." But, Big Sean's rep tells E! News that the tweet was fake...so all is well?
In any case, after Justin was perhaps a little too playful during "Love Me Harder," Ariana let him take the stage solo. "You go ahead and take a break," he encouraged her. "Grab some water or something!"
He hyped up the crowd before launching into his song, "Where Are Ü Now," and showing off some impressive moves alongside his backup dancers. Oh, and unlike last time, he nailed the lyrics—every one of 'em!
Ariana must have liked what she saw, because she rejoined Justin onstage for a joint performance of his 2012 hit, "As Long As You Love Me."
There sure seems to be some chemistry between these two, but Ariana is taken (we know, Big Sean, we know!), and while Justin is single, he's not ready to mingle just yet.
"Well, at this point in my life I'm so focused on myself that I'm not looking for a girlfriend," he recently told USA Today. "I'm just trying to make sure I'm 100 percent so I can add to the person I want to be with."
And when the time comes that he is ready for romance? "I want a girl I can trust, who I can lean on," he said. "This business is hard, and I want someone I can confide in."
"I'm still young," noted the 21-year-old singer. "I'm still trying to figure out who I am, and I'm just trying to have fun."
(Originally published April 9, 2015 at 7:01 a.m. PT)