Cave Story Guide — Know the Branches and Missables
Last Updated: August 16, 2026
Bottom Line: 2 Things to Know First
① Only 1 of the 3 Polar Star upgrades can be chosen. The choice cannot be undone.
② Do not talk to Professor Booster in the Labyrinth.
Talking locks you into v0.8; ignoring him gives superior v2.0 later, also required for the True Ending.
The first basic weapon. Modest power and range, but straightforward shots make it easy to handle. Unlimited ammo. Levels increase damage and range. It branches into 3 upgrades.
Obtained: A chest in the Hermit Gunsmith's room in First Cave. Obtained as part of the story.
Low damage per shot offset by rapid fire. At level 3, firing downward keeps you airborne through recoil; Turbocharge enables extended hovering. Stronger as a movement tool than an attack. Ammo regenerates when not firing.
Obtained: After fighting Curly at Sand Zone Residence, talk to her and trade the Polar Star.
⚠️ Choosing this prevents obtaining Snake/Spur. The trade cannot be undone.
The game's only weapon that shoots through walls. Wavy shots and rapid fire maintain a barrage. Unlimited ammo.
Obtained: Combine Polar Star and Fireball at the Labyrinth Shop.
⚠️ Choosing this prevents obtaining Spur and consumes Fireball, making it unusable.
Considered the completed Polar Star. Unlike others, its level rises by charging rather than weapon energy, so hits do not cause level loss. Level 1 equals Polar Star level 3 in damage. Reliable for late-game play.
Obtained: After obtaining either Booster v0.8 or v2.0, have the Hermit Gunsmith in First Cave modify it.
⚠️ Unavailable if you chose Machine Gun or Snake.
Damages the impact point and surrounding area. Limited ammo, replenished through enemy drops or refill stations. Ineffective against some monsters. Limited usefulness before upgrading.
Obtained: A chest in the Egg Observation Room in Egg Corridor, among other places.
Greatly increases damage per shot and projectile speed. Reliable against bosses; watch ammo.
Obtained: The chest that falls after the Balrog battle in Boulder Chamber.
A fireball that arcs and rolls along the ground. Climbs slopes and bounces off walls for terrain-based attacks. Unlimited ammo, but at most 4 projectiles on screen.
Obtained: Talk to Santa at his house in Grasstown after giving him Santa's Key.
⚠️ Unavailable after using it to create Snake.
At level 3, bubbles surround you as a simple barrier and fire together when you release the button. Maintain level 3 for combined offense and defense.
Obtained: The fireplace in the Assembly Hall in Mimiga Village. Requires Jellyfish Juice.
King's keepsake. Levels 1–2 throw a sword; level 3 repeatedly slashes around the impact. Level 3 suits minor enemies; level 2 suits bosses.
Obtained: Talk to King after Toroko+ in the Sand Zone Storehouse.
High damage per shot and long range, but reverses the normal rule: higher levels make it weaker. Deliberately avoid leveling it.
Obtained: The Clock Room on the Outer Wall, among other places.
① Labyrinth
In the room after Monster X, proceed to the right door without talking to Professor Booster after he falls from above. Jump from the red mark beneath you to clear the gap. Talking makes the professor disappear.
② Core
Pick up the Tow Rope at the map's lower right before fighting the Core. After defeating it and the air-depletion event ends, examine Curly and tow her. Safest to get the rope before battle: it cannot be obtained during combat or after the event.
③ Waterway
In the Waterway Cabin at the upper right of the jellyfish-filled section, examine bed → computer → right bookcase. Then examine Curly 3 times and choose No when asked to leave her. Curly is swept away during Ironhead, but you reunite later.
④ Plantation
At the lower right, talk to Curly in bed, then hear about the memory-restoring mushroom from nearby Cthulhu. Return to Mimiga Village.
⑤ Mimiga Village
Enter the Storage room through the Graveyard's upper-right door. Answer Ma Pignon Yes, Yes, No, Yes, Yes, No. After receiving the Mushroom Badge, inspect it once in your inventory, then talk again to fight. Defeat Ma Pignon to obtain it.
⑥ Plantation
Use Ma Pignon on Curly to restore her memory. Talk again for the Iron Bond. Before boarding the rocket, talk to Momorin and exchange the Mimiga Mask back for Booster v2.0, required for Sanctuary.
⑦ Balcony
If the steps are correct, during the escape after Undead Core, enter the hidden Blood Stained Sanctuary through the save-point Prefab House. Complete it and defeat the true boss for the True Ending. After saving, you may seem unable to leave the Prefab House, but examining the bookcase lets you out.
Only 1 Polar Star Upgrade Path
Machine Gun, Snake, and Spur are mutually exclusive. Trading for Machine Gun prevents the other 2 and cannot be undone. Making Snake also consumes Fireball.
Talking to Professor Booster Prevents v2.0
In the Labyrinth, talking gives v0.8; ignoring him lets you obtain superior v2.0 later. v2.0 is required for Sanctuary and the True Ending.
Tow Rope Timing
Unavailable during the Core battle and after the air-depletion event. Safest to take it before battle.
Leaving Curly Closes the Branch
After examining Curly 3 times in the Waterway, answering Yes excludes you from the True Ending.
Trading the Mimiga Mask Back for the Booster
Before the Plantation rocket, talk to Momorin and get Booster v2.0 back.
No-Damage-Only Collectible
The Alien Medal is obtained only by defeating Ironhead without damage.
| Name | effect | Acquisition |
|---|---|---|
| Map System | Displays a small map. | Upper-right chest in the Shack in Mimiga Village. |
| Life Pot | Single-use full HP restoration. | Talk to Jenka after the event following collection of all puppies in Sand Zone. If you do not have one, a puppy along the rocket's path in the Plantation can also provide it. |
| Turbocharge | Speeds up Machine Gun reloading. | Obtained at Labyrinth Shop while holding Machine Gun. |
| Arms Barrier | Halves weapon energy lost when hit, reducing level loss. | Chest on the upper level of Camp in the Labyrinth. |
| Booster v0.8 | Press jump in midair to rise upward. | Talk to Professor Booster after he falls in Labyrinth B. |
| Booster v2.0 | Move in 4 directions in midair. An upgrade over v0.8. | If you did not take v0.8, obtain it at Arthur's House in Mimiga Village after returning from the Labyrinth. |
| Whimsical Star | At maximum weapon level, creates 3 damaging stars around you. Each hit removes 1. | Obtain at Labyrinth Shop while holding Booster v2.0 and Spur. |
| Nikumaru Counter | A timer specifically for Blood Stained Sanctuary. | Chest in the Clock Room on the Outer Wall. |
Chaco's Lipstick
Chaco's House in Grasstown. Sleep in the bed immediately after examining the fireplace and hearing about Jellyfish Juice.
Curly's Panties
Small room in Sand Zone Residence. Chest beyond a hidden passage.
Alien Medal
Defeat Ironhead at the Waterway's end without taking damage.
Clay Figure Medal
Red Demon in Last Cave (Hidden). Chest after defeating it.
Q. Which Polar Star upgrade should I choose?
The 3 are mutually exclusive; choose only 1. Machine Gun offers rapid fire and hovering mobility; Snake uniquely shoots through walls; Spur levels through charging, so hits cannot lower its level. Spur is convenient for late-game Blood Stained Sanctuary; Machine Gun suits comfortable exploration.
Q. What are the True Ending requirements?
Complete all 7 steps. Five key points: do not talk to Professor Booster in the Labyrinth; get Tow Rope before Core and tow Curly afterward; do not leave Curly in the Waterway; answer Ma Pignon correctly; get Booster v2.0 back before the rocket. The step list on this page gives the detailed order.
Q. Should I avoid talking to Professor Booster?
Not talking is more beneficial. Talking gives v0.8, but the professor disappears. Ignore him and he repairs the teleporter, survives, and later gives superior v2.0. The True Ending's Blood Stained Sanctuary requires v2.0.
Q. My weapon levels keep dropping
Hits reduce weapon energy and levels. Arms Barrier (upper Camp chest in the Labyrinth) halves the loss. Spur levels through charging, letting you fight without worrying about level loss.
Q. Are there irreversible choices?
Yes. Only 1 Polar Star upgrade is possible and cannot be undone. Booster version, Tow Rope timing, and handling Curly in the Waterway directly affect branches. Alien Medal requires a no-damage Ironhead victory.
Q. What is Blood Stained Sanctuary?
A hidden stage accessible only after meeting True Ending requirements. Enter through the save-point Prefab House during the escape after Undead Core. Clear it and defeat the true boss for the True Ending. Holding the Nikumaru Counter records your time.