Bypass Dark Realms
Any of the three Dark Realms can be easily bypassed. This requires some skill, Ako's Purple Vest, all weapons for the character, and all weapons been completely enhanced. Whether or not the gauntlet is completely enhanced is irrelevant. Before entering the Dark Realm, equip either Chigo (for Samanosuke) or Hyosai (for Jacques). The enemies that attack will appear in multiple waves. Just wait for all enemies to appear, then execute one magic attack. Absorb all the souls that appear. Ako's Purple Vest should allow you to do this as many times as necessary. However, if you are fighting large demons, you may need to get up close with either the Tenso (for Samanosuke) or the Enja (for Jacques). Note: A crucial part of this strategy is absorbing the souls. If you feel that you need Ako's Blue Vest as well, make sure to switch back and forth as appropriate. Also, it is much easier to go straight for the bottom part of the Dark Realm that you are in, as the tougher enemies are down there first. By doing this, you can use your magic efficiently on the tougher enemies and not have to worry about the weaker ones.