NINJA GAIDEN Σ

This is for killing 100 enemies using any of the following

Shuriken
Bow
Windmill Shuriken
Incendiary Shuriken
Strongbow
Explosive Arrows
APFSDS Cores
Spear Gun

A certian amount of projectile kills will be almost forced, as the game expects you to use the bow to take out enemies you could not otherwise reach, or tha are not damaged well by melee combat. In multiple playthroughs, this would probably earn you this, certainly if you play Mission Mode (Secrets of Shooting will earn you this 100% by itself).

If you wish to rush earning it, just incorporate projectiles into every combat encounter. In particular, incendiary shuriken, explosive arrows and APFSDS cores will kill most small enemies in a single shot and during the military supply base, can be refilled for free, or bought for 100 (incendiaries and explosive) or 200 (APFSDS) from any Muramasa after they have been obtained once.