Titles (I understand this better now than when I originally wrote the preview a couple of days ago):
Courtier: adults in your clan that you can give jobs to.
Kokujin: control one province. You can assign who controls which provinces.
Master of Ceremonies: does diplomatic actions. You can pick who does this job.
Master of Arms: does military actions. You can pick who does this job.
Master of the Guard: does stealth actions. You can pick who does this job.
Daimyo: controls one region. This, I think, is hereditary and can't be assigned manually.
Clan Leader: runs the clan's army and conducts diplomacy. The next leader is chosen by vote.
Jugoi: a temporary title earned by giving money to the emperor in exchange for honor.
Demesne is how many territories you directly control. You can have five. Having less is OK, but having more will result in revolts. You should pick a member of your clan to administer the "extra" ones as soon as possible.