I'm of the opinion Kenichi is an advanced disciple class fighter. I believe Kenichi is in the upper limit of the disciple class, but still below the expert class. I drawed my conclusions from the statements below:
Akiisame: "In your circumstance, just think of yourself as having become a bit of an advanced disciple."
Miu: "Yes, and also during D of D, even though he did abstain from joining until a certain point, he showed some unbelievable power by defeating the entire enemy team with one finger! Compared to us disciple classes."
I believe both those statements are kind of old now, and did you seriously not read the post above you?
The second one doesn't even sound like it's talking about Kenichi