Enchanted Arms

This is a story line based achievement so you can't miss it. Shortly after fighting the Giggling Man you will encounter Ooka outside the mine by a house. The battle consists of 3 enemies:

Ooka
HP - 2200
EP - 680
Element Type - Wind

Attacks:
Mega Blade - a horizontal sword attack across 3 grid squares
Power Omega - boosts parameters
Impulse - range attack that goes across 4 grid squares vertically
Cross Flare - an EX skill that attacks 5 grid squares in a cross shape.

Blood Fencer
HP - 580
EP - 550
Element Type - Dark

Attacks:
High Blade - a horizontal sword attack across 3 grid squares
X Cutter - a sword attack that attacks the grid square directly in front.

Lord Onyx
HP - 620
EP - 580
Element Type - Dark

Attacks:
High Blade - a horizontal sword attack across 3 grid squares
Impulse - range attack that goes across 4 grid squares vertically

This fight can be easy or hard depending on your level/parameters. Ooka is weak to Earth attacks. And the Impulse attacks are the only attacks aside from Ooka's EX skill that can hit your team if they aren't in the front row. So if you stay out of range you can pick them off with ranged attacks. Ooka's EX attack is strong and can do a lot of damage to your party, Atsuma will take the least damage from it though. Have Raigar use Levitain to boost his parameters and then focus on Ooka with Earth attacks, if all three enemies are in a row have Raiger use High Blade to hit them all. Use Atsuma's EX attack if you can and have your other characters (Yuki and golem or 2 golems) focus on the enemy golems and then focus on Ooka.