Rengoku is one of the coolest and strongest swords in Blox Fruits. It’s a fiery Legendary sword perfect for fighting in the Second Sea, and one of the most popular weapons for PvP combos. This guide explains everything super simply, step by step, like talking to a friend.
Quick Summary: Get to the Second Sea → Farm the Hidden Key at Ice Castle → Find the secret room under the stairs → Open the chest → Enjoy your Rengoku!
What You Need Before Starting
Before you hunt for Rengoku, make sure you’ve checked off these requirements:
- Level 700 or higher: You must be at least Level 700 to unlock the Second Sea.
- Already in the Second Sea: If you haven’t crossed over yet, see the section below.
- Combat-ready gear: Strong fruits, fighting styles, or swords make the grind easier. Even basic gear works if you’re patient.
How to Get to the Second Sea (If You’re Still in the First Sea)
Getting to the Second Sea is not as simple as paying for a boat. You need to complete a short quest chain:
- Reach Level 700. A message will pop up telling you that you’re ready for the next world.
- Go to Prison island. Find the Military Detective NPC standing near the entrance.
- Accept his quest. He gives you a mission and hands you a Special Key.
- Travel to Frozen Village. Enter the cave where the Ability Teacher is located. Find the locked wooden door inside, use your Special Key, and defeat the Ice Admiral boss behind it.
- Return to the Military Detective. Report back to complete the quest.
- Talk to the Experienced Captain. Head to Middle Town and speak with him. He’ll transport you to the Second Sea.
Once you’re in the Second Sea, you’re ready to start hunting for Rengoku.
How to Get Rengoku: Step-by-Step Guide
Follow these steps exactly. No rush. Each step builds on the last.
Step 1: Find Ice Castle
Head to the Second Sea and sail or fly toward Frozen Village. It’s a snowy area with ice everywhere. Right beside it stands Ice Castle, a massive icy fortress with tall white towers, frozen walls, and slippery floors. You can’t miss it.
Step 2: Farm the Hidden Key
This is the trickiest part because the drop rate is very low. You have two farming options:
Option A: Kill regular NPCs (slow but easy)
Defeat Arctic Warriors or Snow Lurkers (both Level 1350) that patrol around Ice Castle. They drop the Hidden Key with less than 1% chance, so expect anywhere from 30 minutes to several hours of farming.
Option B: Kill the boss (faster, recommended)
Go inside Ice Castle and wait for the Awakened Ice Admiral (Level 1400). He respawns approximately every 20 minutes and drops the Hidden Key with about a 5% chance (according to the Blox Fruits Wiki). Server hopping after each kill speeds this up significantly.
Pro Tip: You can purchase the “2x Boss Drops” Game Pass for 350 Robux from the in-game shop to double your drop chances from boss kills. Always activate Instinct (Observation Haki) to see incoming attacks and dodge the Admiral’s ice blasts!
Note: Drop rates are community-estimated and may vary slightly with game updates.
Step 3: Enter the Secret Room
Once the Hidden Key is in your inventory:
- Walk into Ice Castle’s main entrance.
- Head toward the wide staircase near where the Awakened Ice Admiral spawns.
- Look underneath the staircase. There’s a fake wall on the side. It looks solid, but it isn’t.
- Walk straight into the wall. You’ll phase through into a small hidden room with a glowing chest inside.
Step 4: Open the Chest and Claim Rengoku
Make sure the Hidden Key is in your inventory (check the bottom of your screen). Click on the chest to open it. You’ll instantly receive the Rengoku sword!
You’ll also unlock the “Samurai” title (#131) once you equip the sword. It appears above your character’s name.
Step 5: Equip Your New Sword
Open your inventory, drag Rengoku to your sword slot, and equip it. The blade glows bright red with roaring flames. Perfect for showing off.
Congratulations! You now own one of the best swords in the Second Sea!
Rengoku Moveset and Mastery Requirements
Rengoku has two powerful fire-based moves. Both can break Instinct (Observation Haki), making this sword devastating in PvP.
Demon Slayer (Z Key) | Mastery: 150 | Cooldown: ~9 seconds
Dash forward at high speed while slashing 3 times through flames. The final hit breaks enemy Instinct and applies a burn effect for extra damage over 2 seconds. Great for starting combos and catching runners.
Burning Slash (X Key) | Mastery: 300 | Cooldown: ~13 seconds
Tap for a forward fire wave that burns the ground ahead. Hold the key to charge a massive area explosion of flames. Both versions break Instinct. Perfect for clearing groups or pressuring in PvP.
Note: Cooldown times are approximate community estimates. Blox Fruits does not display exact cooldown numbers in-game. Some sources list Burning Slash at 350 Mastery; verify in-game for your current version.
Mastery Tip: Fight weak sea beasts or low-level NPCs repeatedly to build Mastery fast. Unlock both moves to reach Rengoku’s full potential.
How to Upgrade Rengoku at the Blacksmith
You can upgrade Rengoku for a permanent +8% damage boost by visiting a Blacksmith NPC. Here’s where to find one:
| Sea | Blacksmith Location |
|---|---|
| First Sea | Pirate Village |
| Second Sea | Kingdom of Rose (at the docks) |
| Third Sea | Port Town (near the Quest Giver) |
Upgrade Materials Required
Hand over these exact materials for the upgrade:
| Material | Amount | Where to Farm |
|---|---|---|
| Vampire Fangs | 8 | Farm nighttime Vampires on Graveyard Island (Third Sea) |
| Magma Ore | 20 | Drops from Military Soldiers or the Magma Admiral boss in fiery First/Second Sea zones |
| Scrap Metal | 15 | Easiest farm. Pirates and Brutes drop it across all three seas |
The upgrade is a one-time permanent enhancement. Every swing hits harder forever. Totally worth the extra grinding.
Can You Trade Rengoku? (Important)
No. Rengoku cannot be traded. It is a gameplay-earned sword, not a fruit or game pass item. You must obtain it yourself by farming the Hidden Key and opening the chest.
[!WARNING]
If someone offers to “trade” you a Rengoku sword, it is a scam. The only way to get Rengoku is to earn it yourself through the steps described in this guide.
