Demi Lovato Seductively Kisses & Straddles Kehlani On-Stage -- See the Sexy Video!

The 25-year-old singer had promised a 'vulnerable' and 'sexy' tour -- and has apparently delivered.

Demi Lovato told ET to expect a "sexy" and "vulnerable" side to her on her Tell Me You Love Me tour.

On Monday, the final night of the U.S. leg of the tour, the "Sorry Not Sorry" singer delivered at her Newark, New Jersey, show, when opening act Kehlani snuck on stage during Lovato's performance and grabbed her from behind, leading to the two artists sharing a provocative on-stage lip-lock! The surprises didn't end there, as Lovato pushed Kehlani down on the bed -- which served as a setpiece for the performance -- and straddled her as she sang.

It was a very "Cool for the Summer" moment. And a fan caught the unscripted moment on Instagram.

Lovato afterward took to Instagram to celebrate the improvised performance.

"Truly so grateful to have had this extremely special, talented and cool as f**k woman on this tour with me," she wrote. "What an incredible fun sexy crazy night that I’ll never forget!! ???"

Kehlani also posted about the moment, saying on Instagram that it's been a dream touring with Lovato -- and blaming the little stunt on Lovato's dancers.

"tonight your dancers put me up to this but anyone would be stupid not to jump at the chance to hop on that damn moving bed and grab your face looooool," she wrote. "i love you and appreciate you, beautiful. cheers to you, more life and success on the rest of the legs of this tour. ? @ddlovato."

Lovato's tour has been full of big and meaningful moments, including last month, when the singer teared up on stage at her New York City show, where she celebrated six years of sobriety.

"Yesterday, six years ago, I was drinking vodka out of a Sprite bottle at nine in the morning, throwing up in the car," she recalled. "I remember thinking, 'This is no longer cute, this is no longer fun. And I'm just like my dad.' So I took a look at my life, and I said, 'Something has to change. Something has to change, I've gotta get sober' -- so I did."

"The reason I became so open about my story is I know that there are people here tonight that need to ask for help, and I want you to know that it's OK," she continued as the audience cheered. "Mental health is something that we all need to talk about and we need to take the stigma away from it."

Clearly, Lovato's tour has been everything she told ET it would be when she talked to us ahead of her San Jose, California, show in early March.

"We wanted to showcase all aspects of myself as an artist, playing guitar and playing piano," she told ET's Keltie Knight. "Showing a sexy side, but also being vulnerable and open with the audience." 

For more on Lovato's tour, watch the video below.