Hi-Fi RUSH

This is pretty easy. Depending on your playstyle, you may get this naturally, but of not it's pretty easy to farm in only a few minutes.

When you progress through the game and unlock partners, go to the store and buy their respective skill to unlock their parry counter. For Peppermint, that's Kick Shot, for Macaron, Love Tap, and for Korsica, High Alert.

After that, have that partner selected, parry any enemy's attack with (must be on the beat), then exactly 1 beat later, press , and your partner will attack. Look at 808 for a visual of when you should press RT.

If you don't get this naturally before beating the story, you can also do chapter select, and start mission 1. Progress to the first group of enemies. Equip Korsica and use her parry counter. Since she does not damage enemies, you can just stay with this one group of really easy enemies and parry them 100 times for two achievements.