It wasn’t merely “implied” that Ryoken kidnapped Yusaku

It’s straight up what Yusaku thinks. That’s the whole reason he made Bohman name who exactly kidnapped him.

Because Yusaku knows that if he were forced to answer this question, it would be: Ryoken Kogami. Not Dr. Kogami, but Ryoken himself.

So Ryoken isn’t some poor innocent boy who got his new friend taken away. He was an accomplice, and Yusaku knows this.

And doesn’t that make things so much more interesting?