Responses
As far as I understood, he angered and fought with some seniors who got pissed at him and asked help from the "big boss". No matter how strong Ai was, he couldn't fight off a gang of strong seniors at once. And I guess at first he fought back when they raped him, but they probably beat him badly every time. Give in = less pain. Though he did have the knife with him as his last resort.
Why did Ai put up with all of that? At first he fought those guys and, from what I understood, that's why they got pissed at him and things took a wrong turn, but still,
I mean, he's clearly super strong. Why didn't he fend for himself? Why did he just accept "his fate"?