To get several slashes easily, jump and do the UP + SQUARE combo then rapidly press SQUARE to do more slashes.

Unlock the following characters by performing the corresponding tasks:

CHARACTER - HOW TO UNLOCK
Byakuya Kuchiki - Complete Stage 8.
Captain Yamamoto - Complete Stage 7.
Grimmjow - Complete Stage 13.
Hiyori Sarugaki - Complete Free Stage C.
Kenpachi Zaraki - Complete Stage 6.
Kon - Complete Stage 14.
Nnoitra - Complete Stage 13.
Renji Abarai - Complete Stage 5.
Rukia Kuchiki - Complete Stage 1.
Shinji Hirako - Complete Stage 9.
Sousuke Aizen - Complete Stage 13 after defeating him.
Toshiro Hitsugaya - Complete Stage 7.
Ulquiorra - Complete Free Stage D.
Uryu Ishida - Complete Stage 2.
Yasutora "Chad" Sado - Complete Free Stage A.
Yoruichi Shihoin - Complete Free Stage B.