I don't get it. How is 0.1s before your death gonna help you? Won't you still die?

"The Xth Law of the Yama:

As long as one is victorious in one hundred games, one will be able to return to the state one was in 0.01 seconds before death and survive!" (Pg. 2 of Ch. 11)

In other words, even though in this dimension they have already died, if they fulfill these requirements they'll go back in time just a tiny bit and be saved instead - so in the MC's case, all those people trying to find him will get to him in time to resuscitate him.

Also, see shojoshit's post below; I think they explain the concept of the whole story pretty well. (⌒▽⌒)

I think time in the underworld is different from the real world. And if I remember correctly, 0.01 second equals 1 year (?), or perhaps 1 hour ? Anyhow, I'm quite sure that 0.01 second can help one turn back enough time where they can save themselves.