So, I've been doing a bit of *research* on My Tamagotchi Forever, and I think I've figured out how to get the secret character. I think the training course needs to be placed. So I was hoping a few people could do a test the next time they raise a Tamagotchi. Starting when the Tamagotchi is a teen:
1) Place the training course in TamaTown (it actually only needs to be there while the Tama is being fed)
2) Feed the Tama nothing but seafood (let's say the square sushi with the fish on top)
I'll be doing this too. Let me know what happens!