Invulnerable Achievement in Bright Memory: Infinite
Activate "Counter" 100 times
How to unlock InvulnerableTo counter, you'll need to raise your sword with just before an enemy melee attack is about to hit you. If you've done so correctly, the attacking foe will be staggered, opening them up to a counter attack. During a single playthrough, you'll effortlessly bag fifty of these, meaning you'll probably need at least two playthroughs to accumulate 100.