When you break open a crate, barrel, or any other object that makes items pop up, immediately hold Guard. All harmful items, such as the weight or poison, will land on you and disappear without any effect. This also works on helpful items. It works on everything except for bombs.

To unlock pre-made decks play through all the J-Ranking modes.
Clear Point, Elimination, J-Star and Champion Rankings in the J-Arena.

Allen Unlock when you collect more stars than your opponent before the time runs out on the D.gray.man first mission

Don patch Avoid being hit for at least 2 minutes in the 2 mission of bo-bobo

Gohan Clear the stage in 30 seconds or less in the second mission of DBZ

Gon get the most points to win on the first mission in Hunter x Hunter

Hitsugaya Clear Mission 1 of the Bleach Planet with at least 4 points

Ichigo Get the most points on the first mission of the Bleach Planet

Kakashi KO at least 2 opponents with a special attack in mission 2 of Naruto

Kazuki KO all the opponents in the first and only mission in Busou Renkin

Kenshin KO with at least 3X attacks on the first mission of Rurouni Kenshin

Killua Get 4 points more than your opponent in the first mission in Hunter x Hunter

Kyubii Naruto (Demon fox Naruto) unlock Jiraya and evolve him then get the path to Kyubii Naruto

Linali Collect all the stars in 30 seconds on the first D.Gray-Man mission

Nami collect 30 coins In one piece on the third mission

Neuro Complete mission 1 of the Majin Tantei Nougami Neuro

Piccolo Collect All 7 dragon balls on the third mission of DBZ

Renji KO 2 enemies with Special Attacks in Mission 4 of the Bleach Planet

Robin Clear mission 4 of Planet "U" within 30 seconds

Rukia Have a full Special Guage when you clear Mission 3 of the Bleach Planet

Sakura Finish mission 3 of Naruto with full health

Sanji Collect more stars than your opponent before the time runs out on the second One Piece mission

Sasuke KO KO 2 times with an attribute better than the opponent's

Seiya Get the most points to win on the first mission os Saint Seiya

Train Collect more stars than your opponent before the time runs out in the first mission in Black Cat

Vegeta Never use special attacks in Mission two of DBZ

Zoro Get the most points on the first mission on the One Piece planet

Press L or R during the introduction to change the color of the ink you use to scribble on the bottom screen (with the Jump Pirate face). The initial color is white, and the others are black, pink, blue, cyan, green, yellow/orangish, red, and gray.

Hold Up or Down while starting training mode through the deck maker to change it to a knowledge character or Left or Right to change it to a laughter character.

The following are Komas that can be unlocked from doing something other than beating J-Adventure mode missions. The easiest way to get the "Battle times" Komas is to repeatedly fail the "get hit once and you lose" missions in J-Adventure mode.

Goten Help Koma: Battle 200 times
Bobobo Battle Koma: Battle 350 times
Naruto Battle Koma: Battle 400 times
Don Pachi Battle Koma: Battle 450 times
Sasuke Battle Koma: Battle 500 times
Ichigo Help Koma: Get 450 koma
Ichigo Battle Koma: Get 540 koma
Vegito Battle Koma: Get all koma