There's no such thing as fighting dirty against this guy. This was a good start, but an Akemi distraction would've been more effective. Harder to prepare, but Misuzu's mother to disturb him psychologically too; just a recording will do.
Also, you need to start this fight during the beginning of the weekend in the middle of evening just before dinner, after a big meal and long afternoon nap so sleep deprivation and energy reserves are on your side for the long-haul. You can have Akemi bring a bento for him just to further distract him and give him a separate hurdle to worry about, but the food should be laced with laxatives.
Also, also, I don't see any brass knuckles or combat vests, boy.
Well, it's fine. We all make mistakes. You can just try again if this attempt fails. He'll just be a little more on-guard next time, so make this a clean challenge with false honor to throw off expectations.
@KuroAntsatsu Considering his reputation, I wouldn't be surprised if this guy is more vulnerable when he's busy concentrating during meditation than when he's asleep.