Double Soul was first introduced in the two incarnations of Mega Man Battle Network 4. Out of twelve souls, six were exclusive to either game. It appears once more in both versions of Mega Man Battle Network 5. It replaced MegaMan's Style Change capability of previous iterations, and is itself replaced by the Cross System in Mega Man Battle Network 6. Double Soul may also have been the basis for the Trans Arm system from Rockman.EXE Legend of Network.