I was trying to enslave Jane, but in the walkthrough they said that for third class I need flirt, but I aren't able to unlock it, what could I do?
Use your power of Control Magic to become a Hero... Or Villain! · By
they look like a piece of paper, the first one is on floor 3, and you need walk over them, then a short scene should trigger about some teachers secret classes. The next time you enter their classroom you can trigger a scene, where you learn a new spell. I don't remeber where the other notices are, but you can find them if you search every floor. Also the next time you enter the library, a scene with a new girl triggers.
Find a piece of paper in the dungeons until you have 1 secret class for of each teacher, this will unlock a spell in each of the four magic class. Cast spells in there column of magic school to unlock better spells in those magic types.
Cast Suppression to unlock Confusion then on to Charm, then Shrink then Persuade
Cast Speed buff to unlock Stone skin which then leads to Flirt and then into Power Buff
Cast Boost to unlock Grapple then Transform and then Trip
and finally Harm into Torment into Ignite.