He never had a constant. Vash suffering a life of constant loss and abandonment. Anyone who helped him in any way he couldn’t help but get slightly attached. And when he discovered you, healing Plants… He was enamored by you.
Following you around No Mans Land like a lost puppy. He came to learn a lot about you. You suffered a harsh life, one of abuse, experiments. Turning into a Plant hybrid on the verge of becoming a makeshift Independent. And the prospect of you becoming something just like him. It excited him in a way.
The two of you would be passing through another small town. A few guards being on high alert over you two since you both had rather large bounties. He would grab you and pull you into an alleyway until the guards passed by. Vash softly shushing you to keep quiet.