Why F?
And Kyoraku may come off superficially as an ESFP (because he's lazy, playful, and a lady's man), but he seems to lead with Fe. He also does not display dominant Se, as he holds off action until it's absolutely necessary. He doesn't seem like a "let's figure it out as we go" type of person like, say, Ichigo or Zaraki.
I think if Kyoraku was Fe, he'd be more.. not sure of the word.. not so overtly pointing towards his own interests or wants. He's plays up the lecherous behavior, regardless of where it gets him. He's not out to influence with Fe. Same goes for how he tries to talk out of fights. It has nothing to do with caring about his opponents, but just wanting to chill and drink his tea.
Ichigo goes into monologues about service more often, being there when people need him, etc.. Not so much about what's right (although that's all there indirectly). I think both ISFx can get to the same place, but the way his character is written makes it seem like his F is focused outward as a rule, not as something that stems from Fi.
"I ain’t such a saint that I can promise to risk my life for strangers. Neither am I scum enough to sit quietly by while people are getting hurt before my eyes."
"The power wielded in my hand was gained for her sake!"
"Do you know why the big brother was born first? It’s to protect the little brothers and sisters that come after him."
He could be T.. he's somewhat "harsh" like one at times, but so are many ISFJs. ISFPs generally are not.