How it works
One premise in. A project you can ship out.
The hard part of a long story was never the typing. It is holding a hundred thousand words of continuity in your head — who knows what, by when, and what colour her coat was in chapter two — while also being the person who has to write the next scene.
Firn puts five helpers on that problem and leaves every decision with you. You write the premise. They build the world, write the chapters, draw the cast, and read it all back looking for what broke — stopping to show you their work as they go.
You are never handed a finished thing to accept or reject. The work arrives in five passes, and after each one it stops, shows you what it did, and waits.
Free to start. Reflowable EPUB export is free. Full commercial rights to what you make.
You start with a paragraph, not a prompt-engineering session.
The first screen asks for the story, in your own words, at whatever length you have it. Alongside it you pick a format — book, visual novel, comic, manga, or webtoon — a genre, and how much of the work you want Koda to take on. That is the whole setup. There is no template to fill in and no syntax to learn.
If you would rather be asked than to write cold, there is a guided setup that walks the same ground one question at a time, and a gallery of worked examples you can open and take apart.
A glaciologist returns to the research station where her sister vanished ten winters ago, and finds the ice has been keeping a record. Every core sample she drills plays back a moment from that season — but the moments do not match her memory of them. Quiet, cold, character-driven; the horror is epistemic, not monstrous. Two other people are wintering over with her, and only one of them was there before.
That is a real one, typed the way you would type it. Everything further down this page grew from those seven lines.
A bench, not a chatbot.
Ask one all-purpose assistant to do all of this and it drifts, because nothing in it is responsible for remembering. Firn gives the job to five, each with one thing to be good at, all working from the same record of your world.
- The Storyteller
- Keeps your world straight. Who everyone is, where things are, what the rules are, and which promises the story still owes the reader. It is the only one allowed to change your canon, so nothing quietly rewrites your world behind you.
- The Writer
- Gets words on the page. It writes from the outline you signed off and stays inside your canon, so you are editing a draft of your story rather than talking a stranger into it.
- The Illustrator
- Draws your cast, and — the part that actually matters — keeps a face the same face. Your lead looks like herself in image four hundred, not like her cousin.
- The Designer
- Lays out the page. Panels, gutters, where the dialogue sits, and which way the eye travels — left to right, right to left, or straight down a phone screen.
- The Editor
- Reads the whole thing back and finds what broke: a name that drifted, two dates that cannot both be true, someone standing in a room they could not have reached. The catch you would have made on draft four.
Koda is the one you actually talk to. You tell Koda what you want; Koda works out who should do it and comes back to you with the result. You never have to know which of them is holding the pen.
You can see it working.
There are eight of them, and you can always see which one is happening right now — the studio shows the whole track with the current step lit, so you are never watching a spinner and guessing.
- 01
OutlineStoryteller
The shape of the story, beat by beat.
- 02
CharactersStoryteller
Who is in it, and what they are to each other.
- 03
WorldStoryteller
The places, the objects that matter, the rules nobody can break.
- 04
DraftWriter
Chapters you can actually read.
- 05
IllustrateIllustrator
Your cast and the places they stand in.
- 06
LayoutDesigner
Pages that read the way you meant them to.
- 07
ReviewEditor
Everything that contradicts something else.
- 08
PolishStoryteller
The last pass before you call it a draft.
It stops five times, not eight.
Worth being precise about, because it is the difference between a tool that pesters you and one that comes to you when there is genuinely something to decide. The eight steps fall into five passes, and it is the end of a pass that stops and waits.
- BibleOutline · Characters · World
- DraftDraft
- ProseDraft, run again for full prose
- ArtIllustrate · Layout
- PolishReview · Polish
When a phase ends, the run stops and hands you the work.
You are not approving a wall of changes. You are shown what the pass actually made — the cast, the chapter list, the problems it found — and you keep it, change it, or send it back before anything gets built on top of it.
Which is why the order is what it is. You fix a character's name while it lives in one place — not after it has been written into forty scenes and drawn onto sixty pictures.
Firn saves your place before the passes that change the most, so "undo that" is always on the table and always means the same thing.
Your world is built. Here is what I made. Cast 4 characters, 2 with full arcs Places 6 Objects 3 World rules 5 Chapters 12 outlined Saved you can come back to this exact point [ Looks right, keep going ] [ Let me change it ] [ Try again ]
It stops. It does not just tell you it is about to do something — nothing in the next pass starts until you pick.
You choose how much Koda drives.
Three settings, changeable at any point in a project. This is not a tone preference — it changes what the system is permitted to do on its own.
Backseat
You drive the story. Koda rides along, chatting and suggesting, and never runs anything on its own.
Co-writer
Koda builds the story bible — title, logline, and main cast — from your prompt, then stops for your review.
Full autopilot
Koda carries the whole project, pausing for your sign-off between outline, draft, prose, art, and polish.
This is a lock, not a polite request. On Backseat there is simply no way for the crew to start work on its own; on Co-writer everything past the world-building needs you to say go. It is not a tone setting that something can talk its way around on a bad day.
Close the tab. Come back.
Some phases are long. A full prose pass over a book-length project is not a thing you sit and watch, and pretending otherwise would be dishonest about what this is.
So the studio saves as it goes. When you come back it looks at what the bible and the chapters actually contain — not at a stored progress bar, which can lie — and tells you which phase to pick up. Work that finished stays finished. A phase that was interrupted is offered again.
The same is true of art. A render that outlives the run that asked for it is not thrown away; it is collected when it lands and attached to the project it belonged to.
What is not in the studio yet.
Firn is in active development and some of what you might reasonably expect is not here. It is better that you find that out now than three chapters in.
- You cannot import a finished manuscript. You can hand Koda background — canon, worldbuilding, a treatment — and it will build on it. You cannot drop in forty thousand words of existing prose and have them become drafted chapters.
- The formats are not equally deep yet. All of them export. But visual novels have the most built around them — a map of your branches, a full set of expressions for each lead, and a preview you can actually play in the studio. If you want to see Firn at full stretch today, that is where to look.
- There is no desktop download yet. A native app is built but not finished, and we are not going to ask you to install something we have not tested properly.
- It is a first draft, and it reads like one. The Writer gives you real chapters at real length. It does not give you your voice. Every stop, the pen, and the Codex exist for the same reason: you are meant to be in there changing it.