Joseph hissed and decided he would go show the neighbor the best way to introduce the virus. He slithered to the window and opened it before slithering out and immediately closing it again. He didn't want the musk to escape, after all, he would love to smell nothing but his own musk forever.
Joseph quickly slid over to his neighbor's house, and quietly entered an open window. His neighbor was a lazy middle-aged man who didn't do a lot with his life. That meant he was perfect prey. Joseph's neighbor was currently watching a football game on his tv from his favorite chair, whilst eating a bowl of cheese-puffs. Joseph silently slithered behind the chair, coiling his long body just right to restrain his neighbor when he decided to strike. That was right then and there. Joseph grabbed him and lifted his neighbor from the chair, completely cooling his body around him so he couldn't move. They ended up on the floor, with Joseph holding one of his clawed hands over his neighbor's mouth. He hissed quietly into his ear. "Whatever you do next, don't fight it. Give in. It will make you feel good," and with that, Joseph bit into his neighbor's shoulder. His neighbor's scream was muffled by his snake friend's grip, but instead of pumping venom into his neighbor's blood, his mouth injected something more kinky into it. The naga infection allowed Joseph to inject his own semen into his victim's bloodstream.
The semen injected into the blood bulged out of his neighbor's skin like tiny pingpong balls, as the neighbor began to moan in pleasure. Joseph let go of his neighbor's shoulder and turned his victim around to face him. Joseph wanted his new friend to experience an amazing kiss with him, so he held his neighbor--no, lover's, head to face upwards, and opened his jaws to spray cum all over his face. He released his lover's mouth so he could hold it open instead to swallow some cum.
As a result of all this, the about-to-be naga's first change was his head completely losing hair and skin, with his snout growing out so he could look just like Joseph, at least in the facial features at first. Instead of viridian green like Joseph, his new lover's new scales were a desert gold. Happy to see his mate ready, Joseph pulled his lover's head to his own, quickly descending into a deep kiss, their forked tongues interlocking as they sprayed seed into eachother's maws during the kiss. As a result of the new naga's bulging muscles, his clothes slowly ripped apart. Smiling, Joseph positioned himself and began thrusting into his lover hard and deep, whom moaned into the kiss in response. He continued to thrust in and out, the new naga's body becoming more muscled and scaled, his legs melding together and growing longer. Eventually he came to look just like Joseph, but with golden scales. Joseph groaned in pleasure and he thrust in one final time, blasting his seed into his new lover, while at the same time, the naga blasted his seed into the wall. Most of the seed spilled into the naga's hole leaked out, spilling out over the lovers' entangled bodies. They slowly released the kiss, some cum dripping from their maws as they hisses happily.
"From now on, you will be Sssssol. My perfect lover." Joseph and Sol clasped their hands together, wrapping their tongues to one another's. "Yessssss...my perfect love."
After a while, they turned Sol's old house into yet another cum lair, connecting the two houses together by an underground evacuation system. They completely sealed off the other areas of the underground tunnels by hardening their cum and creating walls out of them, just completely submerged the tunnel between the two houses in semen. They swim back through the cum-tunnel to Joseph's house and plan their next move from there, occasionally fucking eachother senseless because of the crazy musk buildup in Joseph's house.