Yamcha was hanging out at Capsule Corp, catching up  with Bulma. They talked for a few hours as the sun set over the balcony. Yamcha yawned and stretched whilst sitting opposite of Bulma.
"You're more than welcome to stay here if you'd like. It'd save you a trip home." Bulma said whilst sipping her coffee. Yamcha took her up on this offer and walked with her to a spare bedroom, opposite Trunks' room.
"Here you go. Theres fresh sheets on the bed." Bulma walked away, hiding her hands in the pockets of her lab coat whilst wistling. Yamcha disappeared into his room. An hour or so had passed and he was stairing at the ceiling. He was rock hard, his cock pinned painfully against his boxer shorts, tenting badly. He heard the door start gliding open, slowly. He saw spikes of purple hair poke in before he saw Trunks' face appear. He quickly sat up and covered his obvieous buldge with the bed sheets.
"Trunks! What are you doing up?" He askes, going red.
"I just wanted to see what you were doing." He says, walking closer to the bed he then decided to climb up and sit on the edge. Yamcha was still resting his hand on his hard cock from under the covers, slowly stroking it. Trunks knew exactly what Yamcha was about to do before he walked in and he wanted to help.
"You know..." Trunks started as he rested his hand on Yamcha's hairy leg. inching closer to his covered crotch. He quickly grabbed the bed sheets that covered his tent and pulled them down. Yamcha's other hand flew down to cover his hard cock, hidden beneath his red boxer shorts.
"I could help you out you know." Trunks says, putting his smaller hands ontop of Yamcha's. Sweat started beading down Yamcha's forehead. 
"W...W-what!" He almsot screetched. Yamcha was never 'cool' when it came to talking about sex. Trunks started to move Yamcha's hands from the tent in his boxers. The long rod was pinned to the left, a wet spot started to form from the head. Trunks reached out and started to stroke the conceiled pole.
"Ooohh!" Yamcha gasped. The only contact he'd had is with Puar, even then he had to convince her to do anything. No one has ever just straight up offered to do anything with him. He could feel Trunks' hands grab onto the waistband and sloly pull down.
"W-what about... Err, Vegeta or your mom finding us?" He stammered and gulped as his boxers slid further and further down. Yamcha's short shaven pubes started to become visable, unlike Vegeta, Goku and Gohan, Yamcha didn't have a treasure trail leading to his belly button. He also had his pubes shaved short, shorter than Vegeta's.
"They're asleep." He says, watching the waistband reveal more pubes until finally the base of Yamcha's dick was visable. Ever since Trunks got fucked by Gohan, he's been trying to get more action with his father, not being successful yet he was extremely horny. More and more of Yamcha's dick was uncovered until the tip finally broke free, slapping Yamcha's abs as a string of pre cum dangled from the tip. Yamcha let out a soft moan as he was full visable to Trunks. The lavinder haire pre-teens hand came up, wrapping around the fat cock. Yamcha's dick was a tiny bit smaller than Gohan's but it was a lot fatter. He was circumcised and had a large bulbous head. Trunks' hand went from the base to the tip, slowly as he started picking up the pace. Yamcha was frozen, getting wanked by Puar was one thing but getting wanked off by someone who had thumbs and were able to wrap their hands around his cock was another. Yamcha's balls were shaven bald, Trunks was staring right at them as they bounced with the force of his handjob. One of his hands went down to stroke the large velvet balls. His balls were about the same size as Vegeta's. Yamcha was moaning quietly above Trunks. The young Saiyan decided to step it up a notch, he leaned over so the cut cock was right infront of him. Yamcha could feel Trunks' breath on the tip of his cock, making him look down. Trunks' mouth opened and the head slowly made its way into Trunks' wet mouth. Yamcha let out a rough moan. As Trunks was going down on Yamcha, one of his hands were stroking his balls whilst he used to other to finger his own ass. Yamcha watched in awe as the younh Saiyan burried more of his cock in his mouth until his nose brushed against the sharp shaven pubes. 
"Oh fuck... I'm gonna cum soon." Hearing this made Trunks op off the dick and stroke it a little.
"In that case, lets step it up." He says with a smug laugh, leaving go of the fat dick, letting it slap back onto Yamcha's abs. Trunks stood up and dropped his own boxers, revealing his smaller cock pointing toward Yamcha with light dustings of purple hair at the base and balls. Yamcha had an idea of what was going to happen next. Trunks got infront of Yamcha on the bed and preceded to get on all fours, showing off his pink hole. Yamcha somehow got harder, his cock started twitching as pre cum left the tip.
"Come on then... Fuck me." Trunks says, looking back to see Yamcha holding his fat cock. 
"Holy shit!" Yamcha said as he got onto his knees, kneeling behind the purple haired saiyan. He pressed the fat, bulbous head of his cut cock against Trunks' tight hole. He applied more and more pressure until the head started parting Trunks' hole.
"Fuck!" Trunks said, taking the fattest dick he's ever seen made its way into his hole, not that he's seen many, only his fathers, Gohan's and Goten's. In no time the massive head parted his ass hole enough to slide in.
"Oohh.. Urghh!" Yamcha let out, feeling a new sensation on his cock, never experiencing something soo tight. He kept pushing until his shaven pubes touched Trunks' ass cheeks. Yamcha's balls slowly pressed against Trunks' then shortly left them. Yamcha started picking up the pace until he was going at a steady rythm into Trunks, slapping his balls against Trunks along the way. 
"Fuck! This is soo good!" Yamcha yelled as he picked up the pace more.
"Harder!" Trunks demanded.
"Oh yeah? I have been trying to do something on Puar lately but she won't let me do it." Everyone had a feeling that Yamcha would fuck Puar but it wasn't known for sure.
"Do it!" Trunks grunted as he was getting pushed against the foot of the bed. Yamcha kept panting as he slammed into Trunks.
"Fuck it... Here it goes!" He grunted.
"Wolf... Fang... Dick!" He yells. His dick started growing longer inside of Trunks as two ball like bumps appeared at the base of Yamcha's dick. Trunks could feel the head of Yamcha's dick change too. Instead of a round, bulbous head, the bottom of it changed into a point, so the tip sloped downwards. Yamcha's dick was turning into a canines inside of Trunks' abused ass hole.
"Holy shit!" Trunks yelled as the dick started to prod his prostate aggressively. Not only did Yamcha's dick change, his attitude changed too. Making him get more rougher as he took on the wolf instinct.
"You like that, huh? You like my long cock in your ass?!" Yamcha yelled, getting rougher by the second. Trunks could only let out rough moans as his body was getting pushed back and forth.
"You want me to knott you, huh? You want all this wolf cock in your ass?" Trunks was soo turned on getting talked to like this.
"Fuck! Do it!" Trunks screamed, knowing it wouldn't wake his parents as their room was on the other side of the large building. Yamcha stopped thrusting and just kept pressing his large cock into trunks. More and more of his cock went into Trunks' ass until he could feel the two large bumps on the side of Yamcha's dick press up against his hole. Soon, the bumps pushed through the hole, resting inside his ass.
"Fuck!" Trunks yelled, his ass has never been stretched this far. Yamcha still had more dick behind the bulbous glands at the base of his cock so he could keep thrusting in and out. About ten minutes went by.
"Fuck... I'm cumming!" Trunks yelled as the tip of Yamcha's newly formed dick slammed into his prostate.  His ass contracted around the canine like cock as white ropes unleashed onto the bed below. The contractions of Trunks' ass pressed onto the round balls on Yamcha's dick, making it impossable to take back out until it softened. The tightness wrapped around his cock was too much and he let out his own blasts of cum in Trunks' ass. Blast after blast entered the tortured hole, splurts of it came leaking out with enough force to slap back onto Yamcha's hips. Yamcha was stuck inside Trunks for a minute or so, until his cock softened enough to take out. Trunks was exhausted after being fucked soo rough by a newly shaped cock. He turned around to face Yamcha, droplets of hot jizz left his ass and trickle down his legs. He saw the dick for the first time. Long and fat and a pointy tip with two bulbous balls on the side, Yamcha's nut sack dangled beneath, emptied. Trunks saw the splatters of cum on Yamcha's hips and some surrounding his cock. Trunks got down and licked the splatters off Yamcha's hips then back to the cock. He sucked the length as much as he could, he could also feel it getting shorter and the head change back into the bulbous tip it was when it entered his hole. He watched as the two round lumbs on the side of the cock disappeared back inside the dick. Trunks finished lapping all the cum up that he saw and climbed off the bed, picking his boxers up in the process. Not saying anything as he left the room.
"Holy fuck..." Yamcha breathed, covered in sweat. He layed back down, resting his head ontop of his arm.
"That was fucking amazing!" He said as he slowly drifted off to sleep, breathing heavily as he came back down from his orgasm. He didn't even bother putting his boxers back on, he just layed there in the nude, letting the breeze brush his moist cock as his balls drooped down onto the bed below.

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