Here is the full list of all 33 Mitsurugi Kamui Hikae achievements. It takes around 8-10 hours to unlock all of the achievements on Windows.
Perform a Flourish
Defeat 100 enemies
Perform a Just Guard
Perform 10 Just Guards
Complete all upgrades
Collect 100,000 SP
Max out Life Gauge
Max out Katana Gauge
Use Zanshin to defeat an enemy
Defeat 10 enemies
String 50 hits
String 100 hits
Perform the holy technique "Celestial Judgement"
Perform the holy technique "Divine Wind"
Reach "Mitsurugi" zeal level
Watch the tutorial
Clear Easy difficulty
Clear Normal difficulty
Clear Hard difficulty
Clear Very Hard difficulty
Defeat stage 1 boss "Kaina" (any difficulty)
Defeat stage 2 boss "Kaiser" (any difficulty)
Defeat stage 3 boss "Suzuka" (any difficulty)
Defeat stage 4 boss "Magatsu Kaina" (any difficulty)
Defeat stage 5 boss "Magatsu Suzuka" (any difficulty)
Defeat stage 6 boss "Magatsu Hino Tsurugi" (any difficulty)
Defeat 1000 enemies
Use Zanshin to defeat 50 enemies
Use Zanshin to defeat 100 enemies
Perform a Counter
Perform 10 Counters
Perform 10 Flourishes
Clear Inferno difficulty