Can be obtained easily if you're doing the winter main story quest: "Tori throwing a tantrum" - you'll be given Lando's Fishing Rod. You can "catch" 4 of the quest-item before completing the quest, exchange the quest item for these knowledges.
This is not well worded (thanks for trying). The key thing is that once you catch the item for Marni, you need to pay with energy for the 4 pieces of knowledge, before you hand in the quest item. Once the quest is completed, you can only get the knowledge if you use another character that hasn't done the main quest.