Quote Originally Posted by http://millenniumwaraigis.wikia.com/wiki/Awakening
Awakening is a game mechanic that is not yet included on the English version but It acts as a second Class Change that gives the Awakened unit a secondary ability, this ability is usually passive. Skill levels are not changed after Awakening, so if a unit has Increase Attack III before awakening they will have Increase Attack III after it as well, so no need to worry about re-leveling skills. Most units do not increase their Unit cost when Awakened, but Heavy armors' unit cost increase by 2 and Samurai's increase by 3, both these units will gain an additional Block . Ninja's cost dereases by 2 after AWK.

Requirements:

The target unit does need to be of Gold or higher rarity

The Unit needs to have 100% Affection/Trust

All units need a Spirit of Awakening, Purchased from the Trading Post for 100 Demon Crystals

Either 200k, 250k or 300k G, depending on if their rarity is Gold, Platinum or Black

3 Class specific Gold Units or CC'd Silver Units

A specific Type and amount of Awakening Orbs, gathered in special Daily missions not available at the moment. The Orbs needed vary in amount between 1(Gold), 2(Platinum) and 3(Black) and the Type depends on the Class, so far there have also been classes that need two types of Orbs

Also there are some special classes, that might not be available for awakening yet, at the time it comes out.
And Skill Awakening comes after that.