As reported by Planet Mega Man, Battle Network 4 for the GBA will be the first game not published by Nintendo to utilize the e-Reader peripheral to enhance the game.

There will be a total of 47 cards in the first series, comprised of 30 "modification cards" and 17 "character cards." An e-Reader+ is needed to use the cards. The cards will be sold in random packs of five starting February 14. A second series is planned to be released some time thereafter.

Modification cards will make Mega Man's attacks more powerful, and the character cards will unlock new characters in the game. There is no word yet on whether or not these features are exclusively unlocked with the e-Reader.

In North America, there is currently e-Reader connectivity with Animal Crossing (GCN), Pokemon Channel (GCN), Pokemon Ruby & Sapphire (GBA), and Super Mario Advance 4 (GBA).

Battle Network 4 was released in Japan on December 2, 2003. There is no word yet on an American release.