Tied by Fate

Unlocking

"Kakarrot, are you going to tell me how you got this strong in 3 fucking years?" Vegeta said from a distance.

Goku jumped with his tail spiking up, not expecting Vegeta to be there still. Goku spoke out his thoughts to Vegeta as he walked to a nearby sofa, "Vegeta?! What are you doing here!? I thought you left with the others!"

Vegeta scoffed, glaring at Goku once again. "As if I had any use to follow them out." He got off the wall he was leaning against, walking toward where Goku was with his tail uncurling from his waist. He reached Goku, pulling his collar harshly and forcing him to stand up. Goku yelped slightly as he did this, looking down at Vegeta as he was much shorter than him as Vegeta increased the intensity of his glare, the room around them increasing with tension. "Now, you better tell me... How the hell did you get so strong in the three years you were gone?!" Vegeta growled out rather angrily.

Goku pushed his arm off, letting Vegeta step back from the strength he used, looking at Vegeta with a bored yet slightly cold stare. "Pretty simple, really. You achieve Ultra Instinct and let your soul handle the rest of the transformations."

Vegeta slightly rolled his eyes, obvious to Goku as he didn't actually believe it. However, he was intrigued by Goku's statement. How did he know everyone had a soul? Were there other transformations that even the legends never spoke of? Vegeta's tail slightly flickered in excitement as it swayed behind him. 

"Now tell me, how the hell did you achieve Mastered Ultra Instinct in the Tournament of Power?" He asked, still slightly annoyed from how vaguely Goku explained how to achieve Ultra Instinct. It didn't make sense to Vegeta that Ultra Instinct was so easy to achieve. Even Goku looked as he had some doubts on the topic. 

As Goku was wiping the imaginary dust off himself, the wagging of his own tail slowing down with his unsureness about the topic, he told him without looking at him directly, "For that, I have no idea, as I wasn't completely conscious when I did it the first time... My mind went on autopilot when I transformed into Ultra Instinct; I couldn't even sense what made me transform into it."

Vegeta was stunned, looking at Goku in slight confusion and anger, his tail stopping and its fur rising. He knew that Goku had his questions about the topic, but he didn't know how to transform it by will? As Vegeta thought that Ultra Instinct was similar to Kaioken, it felt slightly unrealistic as a power-up and not a full transformation. He stared as Goku continued to ramble on, the tail halting its movement, "The only person who knows is my mentor... He's the reason I've gotten so strong nowadays, and I'm not sure if he'd like to talk to you. I think he has some sort of... Grudge? I don't know how to explain it..."

Vegeta instantly knew then he had some form of outside help, his own tail wrapping around his waist and asked him forcefully, "Now let's see whoever your mentor is... Shall we?" He walked to Goku, smirking as he found a way to let whoever his mentor teaches him. "Your mentor seems to be quite powerful. Who is he anyway? And how did he teach you to master Ultra Instinct? Hmm?" 

Goku sighed, realising he had no way to explain it other than to show Vegeta. Goku then led them both outside, explaining, "This might be a shocking thing for you because of how much power I'm outputting to do this, so maybe my mentor or myself could explain it to you if you're interested." When they finally stood outside in the middle of a large fighting area, he got into a power-up stance where he shouted, "Mastered Ultra Instinct! Unfuse!"

Just as he said that, his wristbands glowed grey, and the light that came out enveloped Goku as he let MUI out. The brightness and sheer power radiating from Goku made Vegeta step back, covering his eyes just enough to see him. The grey glow that was on Goku seemingly got taken out, separately forming an orb, separating from him and formed a body similar to Goku's.