Why didn't Masashi Miyamoto take Taira's chip after cutting his fingers? In episode 7 "Virtual bride" of Btooom Masashi attacked Taira with his knife and cut his fingers off. He then caused Sakamoto to fall of the cliff and he kidnapped Himiko. 

Why didn't he take Taira's chip? Why was he left alive?
You could say it is a plot hole. At that point, I don't know why he didn't kill them right there and then.

You could look at it as a typical case of "Bond Villain" where the baddie has to set a challenge/trap for the protagonist without actually killing the girl because it allows the story to continue, and without it your cast of characters thins out, thus ending the story.

Most importantly - in my opinion - The original author was also building that underlying Taira 


   betrayal


story so he can't have him dying just yet.