To get this knowledge, you just have to talk to Tina. And to meet Tina, you need 200 Amity with Fiory next to her.
(Pour cette connaissance, vous devez pour cela débloquer la connaissance de Tina, et pour parler à Tina vous devez avoir 200 en amitié avec sa soeur Fiory à côté)

Need finish ALL the story of keplan, not just the 3 obligatory to meet Flory.

O conhecimento pode ser adquirido ao conseguir 200 de amizade com as duas NPCS (Criadas) que estão próximas a ele, Fiory e Tina

To optain knowledge from this NPC you need to have 200 Amity on both NPC stay nearby (Handmaid) Fiory and Tina.

July 2025: to get his knowledge, talk to Phelix down in Keplan and do his small questline Oze's House and then return to Marco, he will give you knowldedge.