Sage looked down at himself, moving around to get a feel for his new body. As he checked to see if he could still speak, he turned to 420lb Justin, he said "Yo, you still changing or are you good? Luckily I can still talk but I think I'm done." Justin stared into the new stallions eyes and replied "Yea, I think I'm done too thankfully." "Here," Sage said, pushing a hay bale towards Justin, "you should lean over this to help your bloodflow with all that new fat." Justin rolled over and layed stomach down on the bale and sighed out of relief.
Suddenly, Sage's cock sprung out again and his newfound horse libido kicked in at the sight of Justin's plump ass. He trotted over behind Justin and nipped at Justin's back roll. "H-Hey big guy, that's an exit only." Justin said fearfully. "I-I don't think I can resist, I've been attracted to you for the longest time and now I have you in a position to where you can't do anything about it" Sage replied, full of lust. "P-Please don't!" Justin cried out. Sage ignored his cry and promptly mounted him. His cock thwacked back and forth until finally he found Justin's hole and he proceeded to push in. He began to thrust in and out with the ferocity of a wild beast, Justin sobbing the whole time from the pain.
Sage was in ecstasy, he had never felt pleasure like this before, Justin's hole was so tight and warm. Suddenly he felt the climax coming, his cockhead flared and unleashed his seed into his friend, causing Justin's stomach to inflate with gallons of cum. As Sage pulled out, Justin felt his stomach rumble while cum poured out his ass.
He felt like he was on fire as his weight started to go back down, but as he looked down, he noticed his cock was getting bigger. He watched as his cock grew from 7in, 9in, 11, 13, 15; his cock grew both in length and girth (with balls to match) until he was face to face with his cock head. He looked in amazement, but that wonder was cut short as he felt a almost crawling sensation in his back. Sage looked and saw six bumps form on his friends back, and the bumps started to elongate. Justin sat in fear as he could now see the bumps over his shoulder, the bumps had cock heads on the ends. He was growing tentacles. He looked at Sage with a vengeful expression and proceeded to wrap three of his new 8ft tentacles around the stallion. Sage whinnied in fear as Justin brought his other 3 tentacles closer; one positioned near his mouth, another near his asshole, and the last near his massive equine cock. Justin plunged his tentacles into Sage and his eyes rolled in ecstasy, as he could feel every tentacle as if it was his own cock. He thrusted in and out of the stallion with such a speed that Sage was borderline choking. Suddenly, Justin felt a lump in his throat, and it was rising up toward his mouth. He suffocated briefly as his tongue transformed into a cock, matching the ends of the tentacles. As Justin moved his new cock tongue around, all of his cocks erupted in orgasm. They both simultaneously collapsed to the ground in ecstasy and fell asleep from exhaustion.