Told you.
Jack’s just a jobber.
The real final boss of Baki is gonna be Yujiro and Joe William’s son.
Itagaki logic: Jack, Baki, even Yujiro himself, men born from man + woman are just half-assed males with weak testosterone.
But a man born from man + man?
Pure 100% testosterone, the ultimate male.
Obviously impossible IRL, but Itagaki would cook up some bullshit about Yujiro’s god-tier semen rewriting Joe’s body to allow pregnancy.
And hey, parasites exist that turn males into females, so it’s not completely out of nowhere.