I just beat Overlord on Floor 25, then I got a nice wrap up, end credits, and bam, back to title screen. Yet when I look around online I see that the game goes on for another 5 floors and there is a "true" last boss. The game really gives no indication (unless I just missed it) that the player is supposed to return to the game after the end credits roll.
What is the purpose of these 5 floors? Why do they come after the credits instead of just making the game 5 floors longer? I'm pretty satisfied with Etrian Odyssey 2 (ready to move on to 3), so I'd like to know if I can safely move on without missing much, or if it's like a vital/major part of the game to go up through Floor 30 to the "true" last boss.