In chapter 5 of Yakuza: Like a Dragon I was introduced to the job system. If you have played Final Fantasy or Dragon Quest (in fact, Kasuga is inspired by Dragon Quest in the story) then you know the job system already. Not every job is available to every character, but most are available to multiple characters (provided they meet level and stat requirements), save each character's unique job.
Kasuga, as the main protagonist, is well balanced and suited for pretty much any type of job. I currently have him as a Breaker, which is mostly a DPS job. Adachi, an ex-cop, seems well suited to be a tank. I currently have him as an enforcer which is, well, a tank. Both Nanba, a homeless guy, and Saeko, a hostess club's mama, seem suited to be casters. I have them as a musician and a hostess respectively. Both seem to be support/control type jobs, though I am still figuring them out as I just switched to them.