Trek to Yomi

The first enemy is about halfway through the first chapter. Obviously just defeating him is all you need to do. I would suggest using this guy to master the parry (Pressing LB when a sparkle or glint appears on the enemy weapon) as that with a heavy attack (Y button) kills most enemies early on in one hit on normal or below.

Kill First enemy and trophy will pop at the same time.
Here is 100% complete walkthrough guide for every achievement and collectibles in Trek To Yomi:
(Timestamps are in YouTube pinned comment)