Here is the full list of all 14 Okinawa Rush achievements.
Complete a Kata
Get S* rank in the tutorial
Perform a meditation
Parry more than 30 times in one stage
Slam or swing enemies into 3 eggs
Visit the rainbow room in stage 5
Dodge shurikens
Kill enemies with scorpion kick
Perform 100 tombstones
Defeat 50 Samurai
Obtain 10 heads of Rockman
Finish the game on black belt
Beat any stage on nightmare
Collect all 9 endings