The Card Shop at the beginning of the game lets you buy Veedramon and Numemon summon cards. From personal experience... take Numemon's recommendation with a grain of salt. :)

FYI, it looks like there's six "corrupted dungeons" based on the menu graphic I extracted (there's six tilemaps, which gradually show more of this image to the player as you unlock them).
There're a lot more areas than that of course.

Backtracking through one of the "corrupted dungeons" to check NPC dialogue, I came across a Gotsumon that shared my feelings. :)
(I eventually realized the Digivice has a built-in map in this game, which made keeping track of my position a lot easier!)

After a long absence, I'm picking back up the Digimon Tamer: Brave Tamer Wonderswan translation project! Made a good amount of progress the last few days, and really hoping to get it finished this year!