Achievement: Defeat of the King of Knights (over and over again)

[Martha, I'm hilarious]

I've completed the side mission on all chapters trying to get the achievement, but still don't have this unlocked. Aside from just replaying each one again until it does, is there something I'm missing? or some way to tell where it did not count for me?

[naru]

That's how I unlocked her ASAP: https://www.youtube.com/watch?v=9-oVxXAePtQ

[Martha, I'm hilarious]

Originally posted by naru:

That's how I unlocked her ASAP:

Sorry i meant the achievement for doing it 4 times, not unlocking her once.

[「Sh1k1」]

The same process of essentially eating Seiba's food (4-5 yakisoba breads in quick succession) to lure her out and then defeating her has to be done in four specific chapters split out across all four campaigns.

Campaign 1 (Flame Poem): Chapter 4/Ruler Stage, Sector D*
Campaign 2 (Orchid Words): Chapter 2/Nameless Stage, Sector J
Campaign 3 (Dawn): Chapter 5/Cú Chulainn Stage, Sector E*
Campaign 4 (Golden Poem): Chapter 3/Altera Stage, Sector H

The stages marked with asterisks have an extra layer of difficulty, as the required sectors begin under your control, so you need to allow them to be taken by the enemy and then do the required steps to lure Artoria out of her hidey-hole.