Until arriving on Earth, the only touch that Vegeta had known was with hostile intent.
Growing up under Frieza’s thumb, he only felt the hands of another while being punished or carried to a healing pod. Frieza had beaten him within an inch of his life, just to prove he was able, far too many times to count. The only contact Vegeta had known was through violence and carnage.
Immediately upon his arrival in Her home, it was clear She had no personal boundaries. She leaned over him, chest brushing against his shoulder and arm as She showed him the controls of the gravity simulator; She touched the small of his back when squeezing by him in tight spaces; She squeezed his bicep when She found something he said particularly amusing.
Bulma Briefs was nothing like anything he had encountered previously. She made physical contact seem normal— comforting, even.
He made her feel as though every problem Vegeta thought he had was utterly insignificant.
One night, over a bottle of finely aged whiskey, she managed to pry details of the past from Vegeta. He explained some of the terrors he endured under Freiza’s reign, as well as the few memories he held from his time on planet Vegeta. (“Wait— you’re named after a planet?!” was the woman’s first, giggling reply) But, above all, she seemed to sympathize with his plight without pity. That is when he knew he was totally and utterly fucked.
He loved her.
This strange, beautiful, genius, earthling woman who had no reason to show him an inch of kindness. The woman who changed, perhaps even saved, his life. Bulma Briefs. She alone unknowingly taught him what it was to love. Her casual touches and sincere kindness changed Vegeta at his very core, (loathe though he was to admit it) and he knew he would never be the same again.
So, being much more adept at actions than words;
He kissed her.