To unlock additional attacks for certain units, a pilot must achieve a certain kill count before certain scenarios.

Unlockable	How to unlock
Extra Attack for Cybuster, Gaddeath, Zamzeed and Diablo	Masaki, Tytti, Mio and Presia must have a combined total of 100 kills or more before the start of Scenario 17 in Masaki's route.
Extra Attack for Valsione, Granveil and Galguard	Lune, Yang Long and Zashford must have a combined total of 75 kills or more before the start of Scenario 17 in Lune's route.
Extra Attacks for Dygenguard	Sanger must have an individual kill count of 60 or more before the end of Scenario 42.