The pupil chaining or student chaining strategy is for learning spells via the Master/Student Relationship system. A main character takes a mage student, and that student takes a mage student of their own, learns their magic, then teaches 2 forms to the original master.
Examples and referencesEdit
https://www.gamefaqs.com/boards/935234-disgaea-afternoon-of-darkness/53941842 "A good strategy is to have Flonne be a mentor of a Cleric, and that Cleric be a mentor of attack mages. Then your Cleric can learn the attack spells and then also teach those to Flonne"
https://www.gamefaqs.com/boards/589678-disgaea-hour-of-darkness/41281702?page=1 "Learning spells is a chain function. It can be learned by a mentor from a pupil and then that mentor's mentor can learn it from him...and so on."
https://www.gamefaqs.com/boards/589678-disgaea-hour-of-darkness/58016237 "Pupil chaining is mostly useful for passing spells up the chain rather than any stat bonuses."