Reasoning of a Clown
Gamzee had liked Feferi while she was alive. She was always so happy to see him, if not a little creeped out by the smile he always had pasted on his face. When Gamzee found out about her death, he had personally wanted to murder Eridan but Kanaya beat him to it. His rage towards Eridan could be pinned on him being sober once more, but Gamzee knew himself better than anyone. He would visit Feferi's ghost when the comet flew through her dream bubble. She would never seem to treat him any better than any of the other trolls in their group, but Gamzee just liked to see her.
In one of their conversations, Feferi congratulated Gamzee on becoming a God Tier and said that she thought the cod piece addition was really funny and exclaimed that liking cods was one thing they both had in common. He laughed at the joke and told her that she too was really funny. Feferi seemed pleased to hear that because her next action was to hug him and sigh deeply. At this, Gamzee felt strangely warm in the face and hugged her back. They then said goodbye to each other because Feferi had said something about Karkat coming over to talk about feelings and Gamzee didn't want to see his moirail at that point in time because of the whole thing with Terezi.
Karkat still didn't know about the kismesitude, but Gamzee did and it made him feel guiltier with each day that passed. He didn't tell Feferi the reason he couldn't stand to be in the same room as a conscious Karkat because he didn't want Feferi to know that he had a thing with Terezi. That would make him feel even worse. Feferi was one of the few trolls who didn't hate his guts. He didn't want to lose that.
When Gamzee left Feferi's part of the dream bubble, he would slink back into the air vents to be by himself for a while. If he heard Terezi's voice quietly calling to him, he would pretend to not be there for a while and think about his choices. Terezi was good for taking the edge off and making him feel less empty inside for a while, but when all was said and done, it was just a kismesitude. Gamzee kind of felt that maybe if he had a matesprit he wouldn't feel so bad all the time. A moirallegiance was good for that, but his was slowly deteriorating and he couldn't possibly tell Karkat about his troubles. He had to leave.
He told Feferi that he wouldn't be visiting her dream bubble for a while, if they ever crossed paths again. She said she was sad to hear that and asked why. He replied with a generically cryptic response followed by a smile and a wink. She frowned and pouted at him. He bent down to give her one last hug, taking in the salty smell of seaweed from her hair. After that, he pulled up his hood over his head, and horns, then made his way for the one place on the comet where he kept all of his stuff. After gathering up all the things of importance he needed for future guidance of others, he quietly left without a trace.
If anyone asked where he went, nobody would be able to answer them. It was the perfect strategy for leaving that place in his dust. Sure, he would miss Karkat and Terezi and the odd talks he would have with Rose, but the pressure was getting to him and he needed to sort out his feelings and his thoughts. Maybe if he had stayed Rose would be able to help him work it out, but there was an even more important reason for leaving. But he wouldn't delve any deeper into that train wreck just yet.
He had met with Jane Crocker, the human. He had prototyped the body parts of Tavros and Vriska together. He thought maybe his best rap bro would like to share the same body as Vriska, but it ended almost as quickly as it begun. He just wanted Tavros to be happy.
He then met with Jake English, the human. He remembered the unfortunate murder of Feferi, the fact that Feferi had once dated Sollux and contemplated on how hard it was to stand Jake before prototyping "Mr Erisol". Seeing the combined reactions of Eridan and Sollux toward Jake and the utter presence of each other made Gamzee uncharacteristically delighted.
He met with the next human, Roxy Lalonde. He thought carefully about who he would choose to be prototyped. Roxy was definitely a cat person, so Nepeta was a must. If he also prototype Equius it would certainly be happy for the moirails. But then Feferi would be left on her own with some human who was probably not fun or interesting. He only did what was right, and prototyped together dear, sweet, precious Fefeta. He smiled as he saw how content both Feferi and Nepeta were and how well they would be treated by Roxy.
Finally, he visited Dirk Strider, the human. Dirk seemed to have plenty of other halves for the prototyping process, which made Gamzee feel less guilty about leaving Equius by himself in the kernelsprite. At that, Gamzee left the humans to go onto his greater purpose; the cherub.