The Moon Slayer, also known in-game as Kokushibo Sailor Piece, was released during the Moon Update on March 31, 2026, and is the highest-damaging melee style in the game. This is the guide to all the requirements, the best drop rates, the fastest method of getting the Upper Seal, the position of all the NPCs on the map, the steps of unlocking F move, and the build that allows Moon Slayer to reach 15 billion damage on the ultimate.
All Requirements for Kokushibo Sailor Piece Style and F Move Combined
Wondering how many Upper Seals you actually need to fully unlock Kokushibo in Sailor Piece, including the F move, before you start farming? It is 110 in total, and being aware of that figure before you press a button on an enemy alters your whole strategy of preparation.
Before farming a single Upper Seal, understand the full cost across both unlocks, so you know exactly what you're working toward.
Moon Slayer base style purchase from Moon Slayer Trainer NPC on Boss Island:
| Item | Quantity | Source |
| Six-Eyed Demon Title | 1 | Moon Slayer boss drop |
| Gems | 37,500 | Codes, chests, enemies |
| Moon Crest | 1 | Moon Slayer boss drop |
| Crescent Shard | 4 | Moon Slayer boss drop |
| Lunar Essence | 9 | Moon Slayer boss drop |
| Demon Remnant | 16 | Moon Slayer boss drop |
| Upper Seal | 25 | Any NPC across all islands |
Moon Slayer F Move purchase from Slayer F Move Mastery NPC on Boss Island:
| Item | Quantity | Source |
| Upper Clan | Must be equipped | Clan Reroll |
| Moon Slayer style | Already unlocked | |
| Moon Crest | 2 | Moon Slayer boss drop |
| Crescent Shard | 10 | Moon Slayer boss drop |
| Upper Seal | 85 | Any NPC across all islands |
Total Upper Seals required: 110. The F move also grants a permanent +30% damage buff to Moon Slayer. It is not optional if you want the style performing at its ceiling.
Boss Drop Rates: What You're Actually Farming Against
The Six-Eyed Demon Title and Moon Crest are your two bottlenecks. Every other item drops at a rate that most players clear within 20 to 40 boss kills. These two require significantly more patience.
| Item | Normal Drop Rate | Notes |
| Six-Eyed Demon Title | 0.30%–0.88% | Pity guaranteed at 155 kills |
| Moon Crest | 0.30%–0.88% | Need 3 total across both unlocks |
| Crescent Shard | 0.70%–2.09% | Need 14 total |
| Lunar Essence | 3.08%–9.15% | Farms relatively quickly |
| Demon Remnant | 8.91%–26.48% | Fastest drop of all items |
| Moon Outfit | 0.81%–1.22% | Accessory 107% DEF, 85% DMG, 15% DMG reduction |
Greater difficulty summons increase every drop rate but cost more Upper Seals per spawn. Use Extreme or Hard difficulty only if your build clears 1.25 billion HP fast enough that the per-kill cost remains efficient. Auto-spawn is available in the summon menu if you have a large Upper Seal stockpile and a strong AoE build. Enable it and let the farm run passively.
Critical rule most players miss: You must deal at least 10% of the boss's total HP to qualify for any drops. If other players are joining your summon, confirm your damage contribution before the kill registers. Private server farming eliminates this risk.
Step 1: Farm 110 Upper Seals Before Anything Else
Upper Seals drop from every NPC in the game, but the drop rate increases significantly with enemy level. Do not waste time on low-level islands.
Best farming locations ranked:
| Location | Enemy | Level | Method |
| Lawless Island | Arena Fighter | 12,000 | AFK with auto-skills best overall |
| Ninja Island | Ninja | 11,500 | Active or AFK, strong alternative |
| Soul Dominion | Quincy | 10,750 | AFK friendly if already unlocked |
Lawless Island Arena Fighters are the current best source, Level 12,000, with fast respawn timers and the highest Upper Seal density in the game. Enable Auto Skills and Auto Haki, run your strongest AoE build, and stand in the center of the spawn area. Aim for 110 Upper Seals before touching the boss. Having a full reserve means zero interruption to your boss's farming loop.
Stack luck before starting. The Fortune Rune, luck-boosting titles, and the Upper Clan passive (+12% luck) all increase your Upper Seal drop efficiency. The Radiant Rune from the Infinite Tower is also a strong luck option if available.
Step 2: Spawn and Farm the Kokushibo Boss
The Moon Slayer boss is on Boss Island. Talk to the Boss Summoner NPC, scroll to Moon Slayer in the summon list, and submit the required items.
Summon costs by difficulty:
| Difficulty | Upper Seals | Money | Gems | Benefit |
| Normal | 1 | 700,000 | 700 | Default manageable |
| Hard | More | More | More | Higher drop rates |
| Extreme | Most | Most | Most | The best drop rates require a strong build |
The Moon Slayer boss has 1.25 billion HP on Normal difficulty. Team up with two or three players for faster kills the 10% damage threshold still applies individually, so confirm your contribution before every kill. Use private servers to avoid having your drop contribution diluted by random players.
The Six-Eyed Demon Title carries a confirmed pity system it is guaranteed to drop by your 155th kill. If you hit 100 kills without it, do not stop. The pity catches you before 155 regardless of previous luck.
Step 3: Unlock Moon Slayer at the NPC
After collecting all base style items, teleport to Boss Island. From the spawn point, run straight to the opposite end of the island. The Moon Slayer Trainer NPC sits on a rock along the coast. Interact and hand over all items to unlock Kokushibo Sailor Piece immediately.
Step 4: Roll Upper Clan and Unlock the F Move
The F move requires Upper Clan to be actively equipped, not just owned. Upper Clan is a new Legendary clan added in the Moon Update with these stats:
- +40% damage
- +12% melee damage
- +12% luck
- Upper's Wrath passive: 20% chance per skill use to trigger +25% extra damage for 8 seconds
The fortune enhancement of Upper Clan is especially useful when farming the bosses; it directly increases the chances of getting all the items, such as the Moon Crest and the Six-Eyed Demon Title. If you are struggling to roll Upper Clan through normal Clan Rerolls, prioritize it before heavy boss farming so the luck passive accelerates your entire grind. Need to cover the Clan Reroll cost fast? Buy Sailor Piece items through a reliable marketplace for Gems and rerolls directly.
Once Upper Clan is equipped, return to Boss Island. Climb to the top of the hand structure on the white side of the boss arena. The Slayer F Move Mastery NPC is on the right side at the top. Submit 2 Moon Crests, 10 Crescent Shards, and 85 Upper Seals to permanently unlock the F move and gain the +30% damage buff.
Step 5 Power System and Rampage Passive
Two additional systems from the Moon Update significantly amplify Kokushibo Sailor Piece damage output and are worth unlocking alongside the style.
Power System Lawless Island: Requires Level 11,500 and 5,500 Gems to unlock at the Power NPC on Lawless Island. Power Shards drop from the same enemies as Upper Seals, and you can farm both simultaneously. The Power System provides permanent passive buffs to damage, crit, and other stats that stack with all existing build elements.
Rampage Passive Judgment Island: A new Mythic Spec Passive that provides +15–30% damage, +2–4% crit rate, and +5–10% crit damage. Stacks with successive hits and resets after 5 seconds without dealing damage. Pairs specifically well with Kokushibo Sailor Piece's sustained combo-heavy playstyle; the hit frequency of the style's skills maintains Rampage stacks consistently.
Also Read: Sailor Piece Infinite Tower Guide
Full Kokushibo Moveset and Damage Benchmarks
| Move | Effect | Damage Range (Optimized Build) |
| M1 | Wide horizontal moon slash extended range | ~2B per hit |
| Z | Dual crescent beam projectiles | ~3–4B |
| X | Moon circle AoE burst crowd control | ~5–6B |
| C | Multi-slash cone boss rush staple | ~7–8B |
| V | Sustained moon wave field best mob clear | ~8–12B |
| F | Full-screen moon explosion unlocked via F move | 15B+ on optimized build |
Full Melee stat investment is mandatory; every Melee point directly scales all ability damage. Do not split into Sword or other stats. Pair with the Moon Outfit accessory (107% DEF, 85% DMG, 15% DMG reduction) for the highest sustained damage survivability combination currently available.
Best overall build for Kokushibo Sailor Piece: Upper Clan + Fortune or Radiant Rune + Moon Outfit accessory + Rampage Passive + max Melee stats. This combination produces the 100 billion damage potential referenced across community showcases with fully stacked buffs active.
FAQs
How long does it realistically take to farm 110 Upper Seals on Lawless Island?
With a strong AoE build on Arena Fighters and Auto Skills active, most players report 30 to 60 minutes per session, producing roughly 30 to 50 Upper Seals. A dedicated 2 to 3 hour AFK session covers the full 110 comfortably. Front-load this before starting boss farming, so your loop never gets interrupted by running out of summon materials.
Should I farm on Normal or Extreme difficulty for the Six-Eyed Demon Title?
Extreme delivers better drop rates meaningfully, but costs significantly more Upper Seals per summon. Use Extreme only if your build clears 1.25 billion HP in under 2 minutes consistently. Slower Extreme kills consume more resources per drop than efficient Normal clears. Test one, Extreme kill first, and compare your clear time before committing the difficulty change.
Does the Upper Clan requirement for the F move mean I have to stay Upper Clan permanently?
No. Upper Clan must be equipped during the F Move Mastery NPC interaction, but once the F move is permanently unlocked, it stays regardless of which clan you subsequently reroll into. Switch freely after the transaction confirms.
More Sailor Piece Guides:
New to the sailor piece? Check our [Sailor Piece Beginner Guide].
Need free Gems for your grind? Grab the latest [Sailor Piece Codes]
