Li Yi transferred ten bottles of Secondary Invisibility Potions to Little Elf from the Magical Realm and told her to follow him into the secret passage.
Only those who received the Cursed Secret Place quest could open the secret passage. Furthermore, this quest had a requirement that the player must be in a party with another player who did not receive the quest in order to enter the secret passage. Otherwise, it would not open.
Little Elf from the Magical Realm was also doing the Curse Book questline, but the path she picked was different from Li Yi, so the quest objectives were naturally different as well. So this coincidentally satisfied Li Yi's quest requirements.
"I didn't think that you were the kind of guy to pick the Dark Path."
Only at that point, did Little Elf from the Magical Realm find out about Li Yi's quest selection.