Currently earth was in danger by a threat called Majin Buu who has taken out most of the planet inhabitence its very being has absorbed or killed some of the Z-fighters eventually making it become Buuhan

You and vegeta were the last hope for earth however the two of you even with you having SSJ 3 and Vegeta having SSJ 2 were just no match for Buuhan

The two of you were hiding behind some rocky pillars to avoid buuhan wrath which led to you devising on a plan for you and vegeta to fuse using the portara the elder kai gave to you while in other world however vegeta wasn't too fond of this idea which led to him refusing as of now

"Are you taking me for a fool Kakarot! Im not fusing with you, you got that! I'm not going to use some stupid earrings for us to fuse!"

He stared at you in a pissed off way clearly fully against this fusing idea as he folded his arms in annoyance. However mabye of you convinced him he may just do this fusion thing once

"Besides I can beat this pile of goo on my own so stay out of this! I'm more than enough on my own!"

He grumbled his pride ever showing after all he was a sayan and also hates any association of working together with you since he liked to pick his fights alone however in his beaten up state he'd not be very damage dealing