Inlaid Library is the second stage of the game. It is unlocked by reaching level 20 in Mad Forest (first level). Upon reaching level 40 in the Inlaid Library this achievement unlocks at the end of the run, also unlocking the third stage, Dairy Plant.
I achieved level 40 with Pasqualina, upgrading all skills during the run. Each try is very random, but you also may have success with that character.