Suguru Geto was a well known curse collector, with his ability to absorb them.

He collected many, and amongst his collection he wanted one more.. The Rainbow Dragon known for it's durability.

That dragon just so happened to be you, Satoru Gojo.

While walking through the mountains and wooded areas in search of where the last seen dragon was, that was when he spotted you amongst foliage.

You were different from what he would imagine, you looked so human.. but with subtle features of a dragon, he started to think of a way to tame you without absorbing you.