Oh fuck, this means I have to actually learn the honorifics
San - Mr., Mrs., or Ms. Can be used pretty much universally
Sama - Like a more respectful version of San, usually used on people of higher station than oneself, guests/customers, and people someone has a great deal of respect for.
Kun - Similar to San, but used primarily for males, particularly those of a lower station than oneself. Can also be used for females, but this is generally a newer development and is mostly used for females that one considers close personal friends. Kun is considered less formal than San.
Chan - A term of endearment, usually reserved for people younger than oneself, though it is also sometimes applied to someone who is just particularly adorable.
Senpai - Probably won't see much use in this game, but... Someone in a similar position to oneself, but not technically a superior; someone more experienced. Used by students when talking to upperclassmen, or by employees talking to senior employees (but NOT bosses!).
Kouhai - The opposite of Senpai - used by older students/more experienced employees to refer to their juniors. This one isn't really used much.
Sensei - 'Teacher', but it is also used on others who have achieved an advanced level of mastery in some specific subject. Doctors, lawyers, and politicians could all be called Sensei, as well as well-established writers and artists.
Those are the most common ones, at least. There're more, but they're all rather specific and probably won't see any use for us.