Lady Ryuu clearly wasn't expecting Klaus to make such an offer. If there is one thing she knows, then it is the kind of happiness anyone would feel if they had a chance to join the Warrior Tower.
They are a powerful organization whose influence has already reached far and beyond. If he joins them, he is guaranteed to earn more than he would as a freelancer.
Respect, reputation, access, and a whole lot.
Also, joining the Warrior Tower provides some protection that can sometimes go a long way. Naturally, Klaus would be swimming with sharks, but he would have protection against fishermen who would come after him or his family.
The warrior tower doesn't take kindly to anyone coming after one of their own and their family.
So, rejecting all that only to opt to become a freelancer is a bit shocking.
"May I ask why this decision? I know you are angry at what happened a couple of weeks ago. Believe me, I am mad too. However, having a second chance, in my opinion, is better than none.
