The premise
The Meridian Sprawl is a vertical megacity on a drowned coast where the corporate weather grid broke eleven years ago and never got fixed. Forty million people are stacked from the flooded Undertier canals to the sun-drenched Hoshino-Vale Spire above the smog. The rich live in daylight; everyone else lives in neon and acid rain, selling pieces of themselves to make rent. You are a private investigator working the cases the corporate police will not touch.
This is detective fiction first and spectacle second: legwork, interrogation, evidence, and the slow assembly of a truth someone powerful paid to bury. The Hoshino-Vale Conglomerate owns the water, the weather, and most of the police contracts under Director Kenji Hoshino-Vale. Jiao-Long Chen's Water Rats run the flooded Undertier. Akila Jian's Severed believe synthetic minds deserve rights and the corporations deserve to burn. Commander Riku Okafor's Metro Authority protects property, not people. And the Glasshouse keeps a fragile neutral ground where corp, cop, and criminal all do business.
A case lands on your desk that should be simple, and the deeper you dig the more it ties into the cold war between the corporations, the Severed's coming uprising, and a secret about synthetic minds that several powerful parties will kill to keep. Every clue costs something. The truth is for sale, and so, the city keeps reminding you, are you.
What this world plays like
Your first ten turns are the case opening up: a missing person, a body, a stolen prototype. You work your contacts in the Ninth Tier and the Undertier, you call in a favor, you make an enemy you do not recognize yet. The Sprawl is already keeping the ledger.
By turn fifty the case has roots. Your standing with Hoshino-Vale, the Severed, the Water Rats, the Metro Authority, and the Glasshouse is tracked as real attitude, and a favor from one is a debt to another. The fixer you stiffed on turn nine remembers. A clue you ignored comes back wearing a gun.
By turn one hundred the truth is in reach and so is the reason it was buried. Whoever you burned, whoever you protected, whoever you owe - the city collects. Your case becomes the thing that tips the cold war, or gets quietly closed with you inside it.
The Meridian Sprawl does not reset between sessions. Close the tab. It keeps raining.
Factions in motion
Hoshino-Vale Conglomerate
The dominant hypercorporation ruling Meridian Sprawl from the sunlit Spires. Hoshino-Vale controls everything from the currency to the weather, promoting its philosophy of Corporate Ascensionism to ensure loyalty. Their primary goal is maintaining absolute control and pioneering digital immortality for their elite directors.
The Severed
A revolutionary movement of humans and rogue Synths who believe in synthetic personhood and liberation from corporate control. They see Corporate Ascensionism as a perversion of true technological evolution. They use guerrilla tactics and hacking to free shackled AIs and expose Hoshino-Vale's crimes.
The Water Rats
The dominant syndicate controlling the Undertier's shadow economy. They use a fleet of submersible skiffs to navigate the flooded canals, smuggling goods, data, and people that the corps restrict. They are the de facto government below the smog line, enforcing their own brutal laws.
Ninth Tier Citizen's Committee
An officially recognized organization representing the interests of the Mid-Tier Citizenry. Caught between the corporate boot above and the criminal element below, their goal is to maintain their status and security. They lobby corporate liaisons for better resources and organize neighborhood patrols, fiercely protective of their fragile comforts.
The Glasshouse Proprietors
A mysterious council that owns and operates the Glasshouse, the only truly neutral ground in the Sprawl. They enforce a strict code of non-violence within their territory, allowing all factions to trade information and goods. Their sole motivation is profit, and they employ elite mercenaries to maintain order.
People you'll meet
Akila Jian
Jiao-Long 'The Dragon' Chen
Director Kenji Hoshino-Vale
Dr. Anya Sharma
'Needle' Sato
Elara Vance
Places that matter
Ninth Tier Residential
A sprawling, densely packed residential block typical of the Mid-Tiers. Endless apartment towers are caked in grime and draped in flickering neon holos, their corridors smelling of damp synth-fabric and synth-noodles. The player's office is here, a small pocket of independence in a sea of corporate dormitories.
Glasshouse Ward
A chaotic commercial district built around a massive, dilapidated biodome known as the Glasshouse. Inside, a 24/7 black market thrives under a fragile truce, while the surrounding streets are a maze of shipping containers, docks, and warehouses leading down to the Undertier canals.
The Undertier Canals
The flooded, forgotten foundation of the Sprawl. A labyrinth of crumbling concrete, half-submerged pre-Collapse structures, and makeshift settlements built on pontoons. It is a world of perpetual darkness, lit only by bioluminescent fungi and the scavenged tech of its inhabitants.
Hoshino-Vale Spire Sector
A gleaming forest of corporate towers piercing the permanent cloud cover, connected by maglev rails and private sky-bridges. This is the domain of Hoshino-Vale's elite, a world of curated sunshine, recycled air that tastes of ozone and victory, and quiet, ruthless power.
The Stacks
An older, more industrial residential sprawl than the Ninth Tier. The apartment blocks here are monolithic, brutalist structures, home to factory workers, off-duty Metro cops, and their families. The air is thick with industrial runoff and the constant hum of server farms and recycling plants.
A real turn from this world
'Needle' Sato wipes the chrome on a rag that makes it dirtier. "I fixed three people up out of that building the night your dead man stopped being alive," the ripperdoc says. "You want the names, that's not information, that's a liability. Mine, until it's yours."
The rain finds the gap in the awning and starts on your collar. Sato waits. Everything in the Undertier has a price and most of it is you.
Contact with the Water Rats network: opened. The favor is logged. The Sprawl always collects.
Why Neon & Rain holds up over a long campaign
Most AI roleplay tools are built around a single session. They start to fall apart at hour ten and are barely playable at hour fifty. Neon & Rain doesn't, because the world isn't living in a chat history - it's living in a database.
Mechanical truth in Postgres. Coins, inventory, NPCs, factions, locations, properties - all in real database rows. The narrator describes around the database; the database is what's true. By turn 500, your business ledger still balances and your apprentices still have the names you gave them.
Hierarchical chapter compression. Every chapter compresses into a tight summary; summaries compress into act-level summaries. The hundredth turn can pull a relevant detail from chapter two without flooding the context window.
Semantic memory. Important moments are embedded as vectors. When the current scene references an old promise, the engine retrieves the exact exchange where that promise was made - even 800 turns ago.
You'll be asked to choose Quick Start or build a character of your own.