Mega Man Battle Network 4

MegaMan Battle Network 4 is the fourth game in the MegaMan Battle Network series. Like Battle Network 3 before it, Battle Network 4 has two different versions, Red Sun and Blue Moon, that differ only in minor story and gameplay details. Battle Network 4 is compatible with the e-Reader, and can be linked up with Real Operation and the Battle Chip Gate for NetBattles, they are present in the English versions.
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