Bosses in Kaizen are the primary source of XP, Mastery XP, and rare loot. Defeating them rewards you with a Boss Chest alongside a chance at exclusive accessories, crafting materials, and weapons. The game splits its bosses into two distinct categories — Story Bosses and World Bosses — and each type follows different rules for spawning, respawning, and loot eligibility.
Quick answer: Story Bosses respawn within 1 to 5 minutes of defeat at fixed locations. World Bosses respawn 10 minutes after defeat but may have low spawn chances, requiring server-hopping. You must deal at least 15% of a World Boss's max HP to receive any rewards.
Story Bosses — Locations, Drops, and Drop Rates
Story Bosses have permanent spawn points and are tied to quest progression. The in-game quest indicator will guide you directly to each one. Every Story Boss awards XP, Mastery XP, and a Boss Chest on defeat, plus a chance at one or more unique items.
| Boss | Spawn Location | Notable Drops |
|---|---|---|
| Cathy | Jujutsu High Headquarters | Furr Coat [Accessory] — 30% |
| Raiken | School Track & Field | Brace Knuckles [Accessory] — 70% |
| Grasshopper | Lotusgrave Swamps | Grasshopper Wings [Accessory] — 10%, Grasshopper Core [Material] — 42.5% |
| Shroom Chief | Mizuka Outskirts | Shroom Chief Core [Material] — 45%, Mushroom Gauntlets [Accessory] — 10% |
| Lizard | Mizuka Outskirts | Lizard Core [Material] — 25%, Lizard Furr Coat [Accessory] — 10% |
| Cyclops | Mizuka Mines | Cyclops Core [Material] — 25%, Eye Pendant [Accessory] — 8% |
| Frog King | Lotusgrave Cavern | Frog King Core [Material] — 35%, Frog King Crown [Material] — 3.1%, Frog Crown [Accessory] — 9.2% |
| Cave Mole | Cursed Caverns | Cave Mole Core [Material] — 45% |
| Frostbound Titan | Frozen Peak | Frostbound Titan Core [Material] — 45%, Frost Pauldron [Accessory] — 10% |
| Toxic Waste Curse | Toxic Waste Room | Toxic Waste Core [Material] — 45%, Jaw Mask [Accessory] — 8.4% |
| Finger Bearer | The Bearer's Hollow | Finger Bearer Core [Material] — 20%, Cursed Finger #1 [Material] — 2.6%, Red Claws [Accessory] — 6.2% |
| Grin Curse | Shibuya | Prayer's Beads [Accessory] — 5.3% |
| Ironclad Gnasher | Shibuya | Ironclad Gnasher Core [Material] — 45%, Ironclad Gauntlet [Accessory] — 4.5% (also grants 149,700 XP) |
All Story Bosses respawn within 1 to 5 minutes after being killed. Simpler bosses like Cathy come back almost instantly, while bosses that carry rarer loot — Grasshopper and Finger Bearer in particular — sit closer to the five-minute end of that window.
World Bosses — Locations, Drops, and Spawn Behavior
World Bosses are significantly tougher and rarer than their Story counterparts. They spawn at specific map locations but do not appear on every server, and some have notably low spawn chances. Each World Boss also awards XP, Mastery XP, and a Boss Chest alongside its unique drops.
| Boss | Spawn Location | Notable Drops |
|---|---|---|
| Uraume | Frozen Peak | Frost Fangs [Weapon], Uraume Core [Material] |
| Eso | Jujutsu Headquarters | Blood Scythe [Weapon], Eso Core [Material] |
| Gojo | Horobi Village | Binding Vow Spins, Six Eyes Essence [Material], Gojo Headband [Accessory] |
| Sukuna | Shibuya | Binding Vow Spins, Cursed Finger #3 [Material], Malevolent Flame Pauldron [Accessory] |
| Itadori | Trial of Absolute Focus | Binding Vow Spins, Black Flash Essence [Material], Demon Arms [Accessory] |
World Bosses respawn 10 minutes after defeat. However, Itadori and Eso have particularly low spawn rates, so you may need to hop between servers to find them active. Uraume's HP also scales with the number of players on the server, which means fighting with a smaller group of two or three people can make the encounter much faster and more manageable.
15% Damage Threshold for World Boss Rewards
Simply being present when a World Boss dies is not enough to earn loot. You must personally deal damage equal to at least 15% of the boss's maximum HP. If your total damage contribution falls below that threshold, you receive nothing — even if your team finishes the fight. This makes it important to bring a strong build and actively contribute rather than relying on other players to carry the kill.
How to Get Binding Vow Spins
Binding Vow Spins are one of the most sought-after rewards in Kaizen. They drop exclusively from three World Bosses: Gojo, Sukuna, and Itadori. The only other way to obtain them is through Robux. Because all three of these bosses are high-difficulty World Bosses with limited spawn availability, farming Binding Vow Spins requires patience and repeated server-hopping.
Core Materials — Story Bosses vs. World Bosses
Core materials are essential crafting components, and nearly every boss in the game can drop one. The key difference is rarity versus reliability. Story Bosses drop lower-tier cores at relatively generous rates — many sit around 25% to 45% — and since these bosses respawn quickly, you can grind them efficiently. World Bosses drop higher-rarity cores, but the chances are much lower and the respawn timers are longer, making each attempt more costly in terms of time.
If you need a specific core, check the tables above to identify which boss drops it and weigh the respawn time against the drop percentage. For bulk farming of common cores, Story Bosses are the clear winner. For rare materials like Uraume Core or Eso Core, you'll need to commit to the World Boss grind.
Tips for Efficient Boss Farming
Bosses in Kaizen can be cornered and combo-locked using M1 attacks and non-launching skills, which prevents them from fighting back effectively. Luring a boss into a wall or corner and chaining attacks is one of the fastest ways to take them down, especially for World Bosses like Uraume where HP scales with server population.
For World Bosses with long respawn timers, a useful strategy is to have one account remain on the server to hold the instance while the boss respawns. Once the boss appears, the rest of your group can rejoin. This preserves any active drop-rate boosts and avoids wasting time in empty lobbies.
Partying up with other players doubles quest rewards, making boss farming even more efficient when you turn in boss quests alongside the kill. Between the XP, Mastery XP, Boss Chests, and material drops, bosses remain the single best progression mechanic in Kaizen from early game through endgame.
