Digimon World Dusk: InsectPlant Quest: Find an L-Mushroom.

This time, go talk to Lillymon and accept the quest. Find Tanemon in Dark Square. She will tell you to go to Chip Forest to find an L-Mushroom.

When you reach there, go to the treasure box with Novice Cloak in it on your north. Move down to southwest to the next screen. Move to a bit left for a chest contains Forest Key, then walk all the way down to the next area. Move to southwest until you see a blocked door. Ignore it first, instead walk northeast into a dark area. The Digimon(s) here will be a lil bit stronger compared to any other lighted areas, so this is an advantage for you to level up your team.

Open the boxes contain a Novice Blade and a GateDisk. Then, go back to the door, open it up with the key and go thru it. Move south to grab L-Mushroom in the box.

There is a black hole portal, DO NOT into there yet! Once your Digimon(s) reach high level of Champion Level, then you can try to explore it. To go to the portal, move southwest and hit it to go back to the city. Talk to Tanemon, then to the Dark Center for 60 Tamer Points, 3280 bits and a Bronze Plate.