Here is the full list of all 55 GetsuFumaDen: Undying Moon achievements.
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Unlocked 5 or more Bludgeons in Refinement.
Unlocked Hawkwing, the Bloodthirsty Blades.
Unlocked 5 or more Battle Umbrellas in Refinement.
Unlocked 5 or more Katana in Refinement.
Unlocked 10 or more Mastery skills.
Unlocked Kashiwamaru, the Bloodthirsty Blade.
Unlocked Foxglove, the Bloodthirsty Club.
Unlocked Kagamigusa, the Bloodthirsty Umbrella.
Unlocked 5 or more Spears in Refinement.
Unlocked Uriwa, the Bloodthirsty Spear.
Activated the final level of Demonization 10 or more times in one game.
Completed Hero difficulty.
Completed Commoner difficulty.
Defeated Evil God Amazu-Tosu for the first time.
Activated Demonization 50 or more times in total.
Reached Cocytus for the first time.
Defeated Getsu Rando for the first time.
Defeated Subterranean Spider for the first time.
Reached the Avenue of Pleasure and Illusion for the first time.
Defeated Nine-Tailed Fox for the first time.
Reached the Frozen Graveyard for the first time.
Defeated Hydra of the Depths for the first time.
Reached The Great Wave of Damnation for the first time.
Defeated Twin Tempest Demons for the first time.
Reached the Misty Peaks for the first time.
Defeated Colossal Centipede for the first time.
Successfully used Slay on a regular stage.
Reached the Hellfire Cliff for the first time.
Defeated Ryukotsuki for the first time.
Traversed the Blighted Foothills for the first time.
Reached the Land of Limbo for the first time.
Completed Veteran difficulty.
Used Souls to raise Main Weapon Rank to 48 or higher.
Used Souls to raise Subweapon Rank to 24 or higher.
Used Souls to perform Vitality Up 16 or more times.
Completed up to the last stage without ever using Souls.
Completed the game within 30 minutes.
Completed the game while only picking up main weapons and subweapons at your base.
Unlocked 5 or more Dual Wield Weapons in Refinement.
Unlocked 5 or more Gauntlets in Refinement.
Unlocked Myoga-no-Ken, the Bloodthirsty Gauntlets.
Unlocked all of Getsu Fuma's available Training skills on Commoner difficulty.
Activated Flash 500 or more times in total.
Activated Slay 100 or more times in total.
Died 50 or more times in total.