Big Sean -- Igniting Romance Rumors ... Onstage (VIDEO)

Big Sean and his rumored GF Jhene Aiko added fuel to the fire on Friday night.

The duo -- who make up the group TWENTY88 -- performed their new song "On The Way" at Powerhouse in Anaheim and put on quite the show.

At the end of their performance, the two shared an intimate moment ... followed by goodbye kiss from Jhene as she left the stage.

She wasn't the only one who got some love from Big Sean that night.