Justin Bieber & Kendall Jenner -- Gettin' VERY 'Friendly' ... Or Totally Bangin'

Justin Bieber and Kendall Jenner play by different rules than most of us -- or they're just straight up banging ... because 'just friends' don't take pics like this.

Biebs certainly loves his puppies because he spent a romantic day out near Coachella with three of his current favorites ... he posted the disgustingly cute photos with Kendall and Esther.

Check out JB's hand -- friends don't go for the waist touch and neck sniff just for fun. In other words ... if this isn't for a magazine cover -- pretty sure they're screwing.