Do yourself.

You stick the portal with your genitals onto a nearby wall, then get down on your hands and knees. You spread your cheeks and back up onto your self. You moan as you feel your penis penetrating your own asshole. You rock back and forth, the motion sliding your cock deeper and deeper into your butt with each pass. You feel both the sensation in your anus and your penis, as well as your own balls slapping you in the behind when you bottom out. Before long you're shooting your wad deep into your bowels.