In 20xx...
... the rapid advance of Internet technology has created the "network age." 
Everyone now carries a portable exploration device called "PET." 
This personal terminal is an advanced personal digital assistant. 
Using it, you can make phone calls, send and receive emails, keep 
a calendar, store data, shop online and check news from around the 
world. PET is so convenient and helpful that it has become essential for everyday life!
Every PET uses a personality simulation program called Net Navi(gator). 
By customizing your PET's Navi program, you can give your Net Navi a unique 
personality - and even talk to it! But as the network world expands, network 
crime is raging. Hacking and computer virus epidemics have become major 
issues. At the top of the criminal list is a mysterious organization 
called "WWW" (World Three), a group of incorrigible computer hooligans.
To protect their PETs, people have begun installing Battle Chips - special 
chips encoded with battle programs. When you insert a Battle Chip, you 
can arm your PET to fight off viruses and hackers. This is called 
"virus busting" and has become so important that it is now taught in schools.
Lan is a fifth grade student. His Net Navi (and best friend) is 
Mega Man.EXE. Lan and Mega Man.EXE are both extremely skilled computer operators.
In the world of virus busting, Lan and Mega Man.EXE are about to meet their match...