Moon Slayer is a late-game melee fighting style added to Sailor Piece with the Moon Update on March 31, 2026. Inspired by Kokushibo from the Demon Slayer franchise, it places a sword-like weapon in your hand but scales off melee stats rather than sword damage. Despite the visual similarity to a blade, it's classified as a Spec/fighting style, and it's one of the strongest options currently in the game for both boss farming and AoE mob clearing.
Quick answer: Travel to Boss Island, collect the seven required items (mostly dropped by the Moon Slayer boss), and talk to the Moon Slayer Trainer NPC on the far side of the island to purchase the style for 37,500 Gems plus your gathered materials.
Moon Slayer Unlock Requirements
You buy Moon Slayer from the Moon Slayer Trainer NPC at Boss Island. From the island's spawn point, head straight to the opposite end — the NPC stands on a rock facing the water. Interacting with them reveals the full shopping list. Every material except Upper Seals comes from defeating the Moon Slayer boss, so the grind is self-contained on a single island.
| Item | Quantity | Source | Normal-Mode Drop Rate |
|---|---|---|---|
| Six-Eyed Demon (Title) | 1 | Moon Slayer boss | Low (pity at 155 kills) |
| Gems | 37,500 | Quests, chests, bosses, codes | N/A |
| Moon Crest | 1 | Moon Slayer boss | 0.30% |
| Crescent Shard | 4 | Moon Slayer boss | 0.70% |
| Lunar Essence | 9 | Moon Slayer boss | 3.08% |
| Demon Remnant | 16 | Moon Slayer boss | 8.91% |
| Upper Seal | 25 | Any mob, mini-boss, or world boss | Varies (higher-level enemies = better odds) |
The Six-Eyed Demon title is the biggest bottleneck. It carries an 85% damage buff — the highest title bonus in the game — and has a pity system that guarantees a drop after 155 Moon Slayer boss kills. Plan for a long farming session.
Farming Upper Seals
Upper Seals are a Legendary-rarity item that drops from killing any enemy in Sailor Piece. The drop rate is low on weaker mobs but improves noticeably against late-game enemies. Lawless Island is the most efficient farming spot thanks to the dense Arena Fighter spawns and fast respawn timers. Ninja Island is a solid alternative with comparable enemy levels.
Stock up on a large pile before heading to Boss Island. You'll burn through Upper Seals quickly because they're needed for three separate purposes: purchasing Moon Slayer (25), summoning the boss (1–4 per fight depending on difficulty), and later unlocking the F move (85).
Summoning the Moon Slayer Boss
On Boss Island, talk to the Boss Summoner NPC and scroll down to find the Moon Slayer option. The summoning cost scales with difficulty:
| Difficulty | Upper Seals | Gems | Money |
|---|---|---|---|
| Easy / Normal | 1 | 700 | 700,000 |
| Medium | 2 | 900 | 900,000 |
| Hard | 3 | 1,150 | 1,150,000 |
| Extreme | 4 | 1,750 | 1,750,000 |
The boss has over 1.25 billion HP on Normal, so bring your strongest build. Max your skill tree melee nodes, equip damage-boosting titles and clans, and use your best sword or fighting style before engaging. If your damage output is high enough, you can toggle auto-spawn and let the game repeatedly summon and fight the boss while you AFK — a huge time saver given the number of kills you'll need.
On defeat, the Moon Slayer boss can drop Money, Gems, XP, Demon Remnant, Lunar Essence, Crescent Shard, Moon Crest, the Six-Eyed Demon title, and the Moon Outfit (a Mythical accessory with a 0.81% drop rate on Normal). Higher difficulties improve the odds on every item, especially the rarest ones like Moon Crest and the title.
Moon Slayer Moveset
Once purchased, Moon Slayer gives you six attacks. Although the animations look like sword swings and emit crescent moon particles, damage scales with melee stats, not sword stats.
| Key | Description | Approx. Damage (well-built character) |
|---|---|---|
| M1 | Basic slashing combo with crescent moon particles | Standard melee |
| Z | Forward slash into a somersault strike; character moves during animation | ~2 billion |
| X | Two slashes followed by a continuous forward slashing sequence; stationary | ~2.2 billion |
| C | Lifts enemy with a swing, then fills the area with purple craters (large AoE) | 5+ billion |
| V | Cutscene move — massive ground-level cut that demolishes mobs in front of you | 10+ billion |
| F | Creates a black domain, unleashes continuous slashes, ends with a forward burst | 15+ billion |
The C move is the primary farming tool for mob waves because of its wide AoE. Z and X work better for single targets. Save V and F for boss burst windows — they have long cooldowns but can effectively end a fight in seconds when timed correctly. The F move is locked by default and requires a separate unlock process.
Unlocking the Moon Slayer F Move
The F move is Moon Slayer's most powerful ability and grants an additional +30% damage buff to the entire fighting style once unlocked. To access it, you need to find the Moon Slayer F Move Mastery NPC on Boss Island. Climb to the top of the hand statue on the white side of the boss arena — the NPC sits on the right side of the structure, near the King of Heroes seller NPC.
Submit the following items to unlock the F move:
| Requirement | Details |
|---|---|
| Moon Slayer (Spec) | Must already be equipped |
| Upper (Clan) | Obtained through Clan Rerolls — mandatory, no workaround |
| Moon Crest | 2x (from Moon Slayer boss) |
| Crescent Shard | 10x (from Moon Slayer boss) |
| Upper Seal | 85x (from any enemy) |
The Upper Clan is the main obstacle here. It's a Legendary-tier clan that you can only get by rerolling your clan, and there's no alternative path. Its stat bonuses are substantial on their own: +40% Damage, +50% Max HP, +12% Melee Damage, +12% Luck, and a 20% chance on each skill use to deal +25% damage for 8 seconds.
Build Tips for Moon Slayer
Moon Slayer scales entirely off melee stats, so every point invested in melee nodes on the skill tree translates directly into higher damage across all six moves. Rolling a Damage V passive on the melee slot further amplifies output.
For the Power system (also introduced in the Moon Update), the two Mythical-tier powers worth chasing are Colossus and Cursebrand. Colossus provides a direct boss damage multiplier that pairs naturally with Moon Slayer's role as a boss-farming style. Cursebrand is slightly more versatile for general content. Both are obtained by spending Power Shards at the Power Master NPC on Lawless Island.
Boosting your Luck stat through the Kitsune Race, Runes, clan level, and titles also helps during the farming phase by improving drop rates on every boss kill.
Moon Outfit — Bonus Drop from the Same Boss
While farming the Moon Slayer boss for fighting style materials, you may also receive the Moon Outfit, a Mythical-rarity accessory with a 0.81% drop rate on Normal difficulty. It's not just cosmetic — at base enhancement (E0), it provides 107% Defense, 85% Damage, and 15% Damage Reduction. At max enhancement (E10), those numbers climb to 157% Defense, 125% Damage, and 35% Damage Reduction. If it drops during your grind, equip it immediately for a significant stat boost.
Moon Slayer sits at the top of the fighting style hierarchy in Sailor Piece right now. The grind is real — between farming Upper Seals, repeatedly defeating a 1.25-billion-HP boss, and rerolling for the Upper Clan — but the payoff is a style with the highest damage ceiling in the game, a title worth 85% bonus damage, and an F move that can delete most bosses in a single rotation.