Considering we still have 10 volumes or so to go and two sequels, I'm betting he won't take some seconds more to kill Miyabi in the next chapter.

Stick him with potion and run

Chapters without someone peeing themselves: 27

I know the art in Higanjima isn't the best but my favourite panels are always Master and his log thrusts. It reminds me of Guts from Berserk swinging his Dragon Slayer, you feel the weight and strength conveyed in the art.

Talk shit, get hit

So how about pumping him with the vaccine now and killing him once and for all? I guess that would be too easy though, so Akira would go on running to save his friends, rather than finish off Miyabi once and for all, and put an end to this tragedy.