So, we might have 4 steps to reach the secret pack, all animations are numbered, the Marie riddle is the password for Gate 1 (all of this confirmed by the man himself in his PIXIV), and I am stuck in this for a few hours now, because I am unable to figure out the answer.
I tried "fang, tooth, teeth, time, wisdom, mind, memory, tenacity, knowledge, saw, cutting saw, world, sun, universe, waves, wave, bones, skull, nails, fingernails, nail, music, note, notes, musicnotes, fire, iron, wit, power, determination, resilience, intelligence"
And I am pretty sure a bunch more that I do not remember right now, and of course, this is a multilayered hint.