Shining Resonance Refrain

Advantageous encounters happen when you sneak up and surprise your enemies, though it isn't always guaranteed. It is more likely to happen when you have recently departed from one battle and are granted the temporary invulnerability and invisibility to the enemies. Sneak around the back and then walk into them so when it wears off, you can start the battle. Repeatedly try sneaking up on the enemies for this chance and you should get this decently during Opus 2, if not Opus 3.