Jump Ultimate Stars is basically a beat em up fighter.Sequel to the Jump Super Stars title. It's got all your well known manga/anime characters from the Shonon Jump series.
Unfortunately it's only in Japan.

The game goes around using cards called Komas which can range from your basic fighter,
a summon that will call another character to help, or simple help komas that power up your character. For example the Naruto koma from....Naruto allows the equiped character
to wall jump. While Eve from Black Cat allows you to triple jump.

So basicly it's actually an Anime fighter game that is good.
The game also has Wi-fi but I can't get it to work yet since I can't read Japanese.

So anyone got a favorite character or koma?

My favorite character is 6-Koma Luffy (Afro Luffy)

The Wifi is pretty easy to set up. If you're having difficulty with the language barrier, there is a wireless mode guide on gamefaqs.

My favorite is Bobobo. Not because I've actually played the game. I just really like Bobobo.

For the longest time I've been playing as Sanji (from One Piece), since his special attack can annihilate a group of enemies. Unfortunately, once I got the wifi set up, I found out his huge combo style attack is actually hugely ineffective. I've found myself relying more recently on Hiei, because he can combo very well and has plenty of range in his attacks.

Which anime series are featured in this game?
Exactly how many characters are we talking about here?

mlai
Which anime series are featured in this game?

Pretty much anything from Shonen Jump, like Naruto, DBZ, Bleach, One Piece, Yuyu Hakusho, Bobobo, etc.

Black Cat
Bleach
Bobobo-bo Bo-bobo
Buso Renkin
Captain Tsubasa
Cobra
D.Gray-man
Death Note
Dr. Slump
Dragon Ball
Eyeshield 21
Gintama
Hokuto no Ken
Houshin Engi
Hunter × Hunter
I"s
Ichigo 100%
Jigoku Sensei Nūbē
JoJo's Bizarre Adventure
Jungle King Ta-chan
Katekyo Hitman REBORN!
Kinnikuman
KochiKame
Majin Tantei Nougami Neuro
Midori no Makibaou
Muhyo to Rouji no Mahoritsu Soudan Jimusou
Naruto
Ninku
One Piece
Pyū to Fuku! Jaguar
Rokudenashi BLUES
Rurouni Kenshin
Saint Seiya
Sakigake!! Otokojuku
Shaman King
Slam Dunk
Taizo Mote King Saga
The Prince of Tennis
Tottemo! Luckyman
Yu-Gi-Oh!
YuYu Hakusho

Out of all those, over 300 characters are present in the game in one form or another. Substantially less than that are actually playable characters, and some series' don't have any playable characters at all (particularly the romance and sports stories).

I don't have a favorite character per se. I'm big on mixing it up and trying out new combo's of characters. That's a big part of the fun!
For those who haven't played it, think Smash Bros. more than Street Fighter. Simple controls where a big part of defeating foes is ringing them out, though you can also just get their health bar to zero to kill them as well.

Jump ultimate stars rocks! I like luffy as well