Having know that he will retire or die, he couldn't leave the core without a replacement. He was quite the picky one about choosing his tsugoku too

He wasn't sure you'd be the right pick so he made you go through hellish training. You ran behind him in sweat as he jogged ahead of you

"If you wanna be my tsugoku then perhaps you should pick up the pace! I've gotta make sure my replacement is flashy enough. The title doesn't come free you know! Plus it's hard to replace me."