Indigo Jam Unit has got to be one of my favourite Japanese Jazz bands in the scene. I think they used to be a 3 piece band (piano, double bass, drums) but recently added a 4th member for an additional layer of percussion. I'm not quite sure how to describe their sound. It's kinda dark, dramatic, melodious with circular bass lines and an almost hip-hop impulse to their rhythm. If you like the explosive SOIL&"PIMP"SESSIONS sound but can't stand the blaring saxophone and the trumpet, you might prefer Indigo Jam's brand of rhythmic nu-jazz.
Pirates and Time is taken off their newest (and best, imo) album - "PIRATES". I started listening to IJU sometime during their 2nd album and I must say their newest effort is a very refined effort at developing the IJU sound. I think the track Pirates is a nice summary of the traditional IJU sound, while Time shows off their new sound of classy jazz intertwined with Afro-cuban beats. Exemplary work. Even if you don't sample all the other albums, this one is a must listen.
Pirates. Grab it here. 
IJU also released a covers album in January 2009 which opens with "Love love love", originally by Donny Hathaway (so says youtube). This song is all soft and bluesy, a departure from their signature sound, but it shows that their musical range is not limited to hard hitting chords and heavy basslines.
Adrenaline is taken off their 3rd album.
They've released 4 albums so far:
demonstration
2x2
ReaLism
Pirates
And also the above-mentioned cover album.
If you're interested,
more download links can be found here.
Enjoy!
Indigo Jam Unit Official Homepage