It's not the difficulty level, but rather that you can't fight him unless you meet the specs, and you can't progress, so he's treated as a boss unrelated to the main scenario.
You can fight him in Junk Faure, so try looking for him.
do you plan on reworking Kirisaki then? Hes a pretty lackluster boss because of his lack of vore attacks.
Your game is great though!
