Assassins turn killing into a pure art. They bring death most often by underhanded means, and they have the power to topple entire governments with a single blade. Some form guilds and hire themselves out to the highest bidder, others work within families or clans. In any case, assassins are feared far and wide across Ehrdi.
Shinobi are assassins from the Senjo nation, specifically the country of Senjokuni. They are perhaps the finest assassins in the world -- though, few outside of their clans know anything about them other than they are masters of spying, stealth, disguise, death, and some believe a brand of magic different from any other. Only Senjo, Half-Senjo, and Senjo Humans are Shinobi.
Though not true assassins, most view bounty hunters as such because many famous hunters use underhanded tactics similar to those of true assassins. They kill and capture for the price of the bounty on a target's head; most don't discriminate between their victims, whether they be criminals or innocents that ran afoul with a powerful gang. A few bounty hunters have been known to be rogue justice-dealers, but they are few and far between.