Chisao originally appeared in EXE/BN 3, and was introduced in episode 54 of the anime. Chisao is Dekao's younger brother, and he lives in the city of Amerope. Chisao is currently too young to own a Net Navi, but he long desires for one. He is a very talented Net Battler, he even succeeded in making Gutsman perform a Program Advance!
Chisao sticks around in Axess, while Dekao is in Jawaii. ^_^ This little kid is so very adorable!
Source: Rockman.exe Online