Tobaku Haouden Zero

Tobaku Haouden Zero summary:

Ukai Zero saves three troubled teens from a Suicide Website, and together chooses to work as 'Robin Hoods' of society. However, one of Zero's friends are caught by an organization he got in trouble with, and Zero is forced to enter a gambling competition hosted by a rich, rotten old man who is looking for talented gamblers to be his rep player. The reward money? ONE TRILLION YEN.