Katana ZERO: Complete Guide

This guide covers Katana ZERO's combat and Chronos slow-motion, dialogue choices, every hidden key and the swords they unlock, the achievement list, and Hard Mode and Speedrun Mode.

Researched September 2026 — current as of the latest Steam build (the free DLC is still unreleased; last official word "Still coming. Still free." on 14 April 2025). Live games change; check the linked sources if something differs.

Quick Start

Everything dies in one hit, including you. Each room is a short puzzle, and a death rewinds you to the start of that room.
Chronos (slow-motion) is your main tool. Hold it to slow time. The meter drains while you use it and refills on its own afterward.
Your sword deflects bullets. Slash just before a bullet reaches you to send it back at the shooter. This is the most important skill in the game.
Dodge-roll through danger. The roll makes you briefly invulnerable to attacks, including lasers and melee swings, when timed right.
Throw things. Bottles, knives, busts, and other items you pick up can be thrown to kill or stun from range.
Kill everyone, then leave. A room only counts as cleared when every enemy is dead. Then the "replay" of your successful run plays like a tape.
Dialogue is real-time. You can interrupt people (the red option) before they finish talking. Your choices change conversations, a boss fight, and some achievements.
Look for hidden keys. Five secret keys unlock alternate swords. Several depend on doing something unusual in a level.

Controls

Defaults can be changed in the options. Keyboard and mouse or a controller both work well.

Action	Keyboard / mouse default	Notes
Move / jump	WASD (W or jump key to jump)	Wall-jump by jumping into and off walls
Attack	Left mouse	Attacks toward the cursor. Deflects bullets
Pick up / throw item	Right mouse	Items thrown toward the cursor kill most enemies
Chronos (slow-mo)	Shift	Hold. Limited meter that refills
Dodge roll	Down while moving	Brief invulnerability
Interact	Context-sensitive	Doors, switches, dialogue

If a key is different on your install, check Options > Controls. The mouse aiming model works the same either way.

Core Mechanics

Combat fundamentals

Attack direction follows your aim. You can slash upward to hit enemies on platforms or catch bullets from angles.
Deflecting: Bullets that reach your blade mid-swing are reflected. Chronos makes the timing forgiving, so use it every time several shooters are active.
Attack lunge: Slashing gives you a small lunge. Chain slashes in mid-air for movement, or to close gaps before a shooter fires.
Doors: Kicking or slashing a door open stuns or kills enemies right behind it.
Stairs, lasers, and turrets: Laser tripwires kill instantly unless you roll through them. Some levels have switches to turn them off.

Enemy types

Enemy	Threat	Counter
Grunts / thugs	Melee	Slash first. They're slower than you
Pistol and gun enemies	Single shots	Deflect back at them
Shotgunners	Wide spread	Deflect, or roll in close
Shield officers	Block frontal attacks	Get behind them, throw items, or deflect into their backs
Machine gunners and turrets	Sustained fire	Chronos plus rolling, or break line of sight
Bosses	Unique patterns	Watch one full cycle before committing

Chronos management

Slow-mo lasts only while the meter holds. Use it in bursts: deflecting, crossing tight gaps, handling several shooters.
Rooms often have a natural rhythm. Enter, pop slow-mo for the dangerous second, release, then finish.

Dialogue and story choices

Conversations run in real time. Interrupting (the red option) lets you cut people off, and staying quiet or choosing specific replies gives different results.
The Psychiatrist's sessions change depending on whether you take your medication. "Refused medication" rewards the defiant route.
At least one boss fight only happens because of specific dialogue choices.
The receptionist, the Girl next door, and other characters react to how you've treated them. Play through twice to see the different routes.

Levels and Setting

You play Subject Zero, an amnesiac assassin working through contracts from his Psychiatrist, who doses him with the drug Chronos. The levels are separate contracts with story scenes between them. Places you'll go include the Factory, the Hotel, Club Neon, the Prison, Studio 51, the Mansion, Chinatown, the Slaughterhouse, and the Bunker (two parts), plus variety levels like a stealth section and a motorcycle chase. The Dragon's tape is a special level with its own achievement.

Some sequences have you play as another character. The story ends on a cliffhanger by design ("To be continued" is literally the completion achievement), and the announced free DLC is expected to pick it up. Dialogue choices change scenes, relationships, and at least one boss encounter along the way.

Hidden Keys and Swords

Each key is a hidden achievement that unlocks a sword. Per the community wiki, you can swap swords in the Government Lab level, which opens after you find the Psychiatrist's body in Bunker pt. 2 and complete the game.

Key (achievement)	Hint from the game	Sword unlocked	Sword effect
Prism key	"Most people go right. You went left."	Prism Sword	Kills leave multicolored bloodstains (cosmetic flair)
Master key	"You stopped a suicide. With a murder."	Sword of Masters	Swings fire energy blasts (a Zelda nod), at a slower attack speed than the katana
Prototype key	"Fulfilled your secondary goal in the prison."	Claymore Prototype	Huge cleaver. Longest reach and slowest swing. Crushes bullets and reflects several projectiles
Phoenix key	"Found what the robber left behind."	Phoenix Edge	Shoots a small burst of flame toward your aim. Can set off barrels
Savant key	"Didn't wake up Leon."	Savant Knife	Very fast attacks with the shortest reach. Can reflect automatic fire and hover in mid-air by attacking repeatedly

Finding all five gives Secret hunter. Only Zero uses the unlocked swords; sequences where you play another character keep the default weapon. Tips:

Prism: In a spot where the obvious route goes right, try going left. Explore every junction.
Master: Watch for a scripted moment where someone is about to take their own life, and step in violently.
Prototype: The Prison level has a secondary objective. Pay attention to NPC dialogue and objectives there.
Phoenix: Look for the aftermath of a robbery and search where the robber was.
Savant: Leon is asleep. Don't wake him (stealth through, and don't make noise near him).

Achievements

Achievement	How to get it
Don't hang up!	Hang up the phone a lot
Feline Persuasion	Pet the cat many times
What a bad idea	Jump off the penthouse balcony
Refused medication	Refuse the medication during the story
Party Animal	A dialogue moment about handing over your katana. Choose the bad idea
Coffin Head	Kill a familiar character on the Quiet Hills set (Studio 51)
No love for robots	"Poor guy." A story-moment interaction with a robot
Beatdown	"You ruined his fresh track suit." A specific fight outcome
The End	"Meet your final end in chinatown."
The Dragon's tape	Complete the Dragon's tape level
Forbidden Ultimate Danger Tempest-Eyed MAJORDOMO Imperial Barrage Crab, Evixion	"Your trap card was activated." A hidden gag
Funny prank	Kill yourself in an elevator
Psychotherapy	Defeat the Psychiatrist's final form
To be continued	Beat the full game
Prism / Master / Prototype / Phoenix / Savant key	See the key table
Secret hunter	Find all hidden keys
Hardmode	Complete a full run in Hard Mode
Gold Medal	Get a total rank of gold or higher in a full speedrun

Many of these depend on choices. Keep a note of which ones you're missing and use a second playthrough for the alternate dialogue branches.

Hard Mode and Speedrun Mode

Both came in the May 2019 update:

Hard Mode unlocks after you finish the game and is launched from the Speedrun Mode menu. It adds new enemy types, revamped levels, reworked bosses, and new challenges. Complete a full run for "Hardmode".
Speedrun Mode has timed runs with options for stable enemy behavior, scene skipping, and detailed stats. Runs auto-save, so you can quit and resume. A full-run total of gold or better earns "Gold Medal".
The same update made the optional stealth level more consistent (fixed patrols and more lenient enemies) and added cat petting.

Speedrun and Gold Medal tips

Turn on stable enemy behavior so routes can be repeated.
Learn each room's fastest clear. Thrown items and deflects save a lot of time.
Chronos is mostly for safety, and good routes use it sparingly.
Practice individual levels before a full run.

Common Mistakes to Avoid

Slashing too early at bullets. Swing just before impact, not when the gun fires. Use slow-mo while learning.
Charging shield officers head-on. Flank or throw something.
Running out of Chronos before the dangerous moment. Enter a room calm and save the meter.
Ignoring throwables. Items often clear the hardest enemy in a room safely.
Skipping dialogue options. You miss content and achievements. Try interrupting and not interrupting.
Forgetting to explore for keys. Obvious routes skip the secrets.

Advanced Tips

Door kicks as openers: Open a door into a group to stun them, then clean up.
Mid-air slash chains: Repeated air slashes extend your movement. The Savant Knife takes this to the extreme with its hovering.
Deflect aiming: A reflected bullet travels back along your aim line. Point at a second enemy to get two kills from one shot.
Lasers and rolls: A roll timed right slips through laser tripwires. Practice on the easier rooms.
Try the swords: The Claymore Prototype makes bullet-heavy rooms trivial but slows your clears. The Savant Knife is the speedrunner's toy.

FAQ

Is the Katana ZERO DLC out yet? Not as of this writing (September 2026). The last official Steam update (April 2025) said "Still coming. Still free.", and the 2022 gameplay-footage post confirmed it will be free for all Katana ZERO owners. Askiisoft has talked about its scope in past developer comments, but there's no official release date, so treat any size or story claims as unconfirmed until it ships.

What was "Katana HERO"? An April Fools' 2023 update on a Steam beta branch (code: notthedlcbro), English only. It isn't the DLC.

How long is Katana ZERO? Commonly around five to six hours for a first run. More if you chase keys, achievements, Hard Mode, or gold speedruns.

How do I change swords? Unlock them with the hidden keys, then switch in the Government Lab level after completing the game, per the community wiki.

Is there more than one ending? The main arc ends on a cliffhanger, but dialogue choices change scenes and at least one alternate outcome. Play again to see the other branches.

Is Hard Mode worth it? Yes, if you liked the combat. It remixes levels and bosses rather than just raising damage.