While most Bushi train under a school, others may forgo training and strike out on their own. Those who enter in a school will work to earn the chance to undergo the seppuku ritual to trigger a Locker Ball and turn into a Samurai.
Societal View of Bushi
It is very common for people to confuse Bushi and Samurai as Daruma is impressed when Hachimaru knows the difference between the two.  And even Hachimaru's father Furuta mixes up the two when expressing his dislike of Bushi to the Ronin.