Brain Adventure Record Webdiver (2001)

Original title: 電脳冒険記ウェブダイバー

In the year 2100, children have become Web divers and uploaded their consciousness onto global computer networks. They play in a cyber park called the Magical Gate. One day, a mysterious computer virus appears and begins to destroy the Magical Gate. Programs called Web Knights were created to protect the children from the virus but the virus turned all the Web Knights against the children. The only Web Knight to escape this is Gladion. Gladion seeks the help of Kento Yuki, a Web Diver who is in the fourth grade.