Saru! Money!!

From MangaHelpers:

Sarugutsuwa "Saru" Jyouichi is what they call a "Plant" in the realm of yakuza. These "Plants" are assigned to assimilate themselves in a certain profession, whether a school teacher or banker, and recruit potential candidates into their yakuza clan. Saru has been assigned to become a school teacher and seek students and/or his colleagues that may be of use for his clan. The name of the game is money, and he will use everyone and everything to make money for his clan. [DrCoke]