Defeat the Sieryu leader and go to East Station in Kicking Forest. Go to the machine and it will say that Guilmon possesses a Blue card. Go to Asuka City and enter the Inn. Go into the room full of beds and you will find Guilmon. Talk to him and he will say his cousin has a Blue card and he will be going somewhere to eat. Go to the Forest Inn, and beside the Guardromon you will see a Guilmon. Talk to him and he will say he is in Sieryu City. Go to the Sieryu Inn and talk to the Guilmon on the bed. He will give you a Blue card (which is a fake). Go to East Station to that machine, and it will tell you that it is fake. Return to Sieryu City and you will see a Guilmon on the streets. Talk to him and he will say that Guilmon is a trickster and that he likes to hide in spooky places. Go to the Forest Inn. Go to the bottom floor to find him. Talk to him and he will apologize and give you the Blue card. You can then go to the East Station and go to the South Sector.