When you start a New Game Plus mode (after beating the game once), there is a new set of armor to find: the Dark Armor.

Stats are quite interesting, so it's worth the hunt.
You can get these pieces both in day and night.

ARMOR STATS

• Dark Breastplate
  
  • Power: 9
    
  • Constitution: 5
• Dark Leg Armor
  
  • Endurance: 7
    
  • Constitution: 3
• Dark Armguards
  
  • Aggressiveness: 8
    
  • Constitution: 2

From Pseudo's Training Circle, reach the highest point of Northern Ruins:


From there, just look a little below you: you should see a statue with the breastplate.


Jump down and you'll get the piece of armor.

This piece of armor is found right next to the crab cave in the Zonectic Mountains coming from the Corwid Territory.



After taking the elevator and changing zone, there is an ascending road just to the right:

Follow it and you'll find a statue with the legs part of the statue:

This part is trickier to explain, but easy to find in-game!


Starting from the tend between the Amokuali and the Salt Marshes (were you fought the Beastmaster) change zone and keep turning left.


If you haven't freed that zone from the thorns, then explore it during night then come back, as that area is not immediately reachable the first time you arrive.


Going forward, go to the huts on the left and then climb (you should pass Eo the trader in one of the huts).


When on top, you should see just below you the statue:


Congrats! This is the last piece of the armor! Now you're fully equipped to beat Gemini's a## once again!