One Piece: Gigant Battle 2 - Shinsekai (Nintendo DS)

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Robin/Franky/Brook 2nd support attack

To unlock Robin, Franky & Brook pre-timeskip's second support attack, you must level them up to level 3 in Story Mode. Robin's second attack is "Wing", Franky's is "Ballad" and Brook's is "Yahazugiri".

Thousand Arena - 1 VS 100 challenge

The 1 VS 100 challenge consists in a serial of 100 short fights in which you are alone (without support characters) and not being able to recover between each fight (except that after beating 10 characters you'll be rewarded a piece of meat). This is a hard challenge which demands a lot of concentration and coordination along with luck. To unlock it, you have to finish the Thousand Arena Battle Royale and One To One challenges in Shin Sekai difficulty (Very hard) 5 times each with different characters.

Thousand Arena - Shin Sekai difficulty

You can unlock a new difficulty for the two main tournaments of the Thousand Arena mode (Battle Royale & One To One) named "Shin Sekai difficulty" (Very Hard). To do that, you have to finish the tournament in Grand Line difficulty (Hard) with 5 different characters.

Unlockable characters

Here is a list of characters that can't be unlocked through Story Mode.

UnlockableHow to Unlock
ChoppermanFinish the Thousand Arena One To One in any difficulty with the 45 characters.
Main character support versionsExecute all the character moves in Training mode or finish a Thousand Arena tournament with the wanted character.
NeptuneConnect to the Nintendo WFC and select "Download Content" to unlock a secret level in Story Mode. Finish this level to unlock Neptune.
ShirahoshiConnect to the Nintendo WFC and select "Download Content" to unlock a secret level in Story Mode. Finish this level to unlock Shirahoshi.
Soldier Docking EmperorFinish the Thousand Arena Battle Royale in any difficulty with the 45 characters.