Crystals are a paid currency and one of the primary resources in Future Fight.
It can be used to buy new uniforms and various packages in the store. It can also be used to refresh daily limits in many play modes.
Daily: 25 if all 5 Daily Challenge are completed
Weekly: 30 if 30 Daily Challenges are completed
Monthly Check-In: 100 each on the 10th, 18th and 24th day
Timeline Battle: Variable amount depending on placement each week. Additionally, one-off rewards for winning Timeline Battles, eg 120 for 3000 wins
Quests: Obtaining certain amounts of characters at a certain rank, eg Reach 3* with 30 characters for 30 Crystals
Character Progression: 20 Crystal for each level 50 character, and 40 for level 60 character
Friends: Have 50 Facebook friends for a total of 1000 Crystals, and 150 for 50 ingame friends