15.【Rekiden】Start a Sengoku SLG Just by Pasting a Template into AI

The 1561 Battle of Kawanakajima Scenario

tags: [AI, ChatGPT, Game Design, Sengoku, Simulation]

🏁 Introduction

Do you still think:

“Making a game means writing an engine”?

In this article, I introduce a design where you write no code at all,
and instead use AI like ChatGPT as the game engine itself.

All you need is a single template.

🎮 Conclusion: Paste This Template into AI and the Game Starts

Paste the following scenario template
directly into ChatGPT, Claude, Gemini, or any LLM.

📋 Game Scenario Template (Copy & Paste)

■ Takeda Clan (Takeda Shingen) Template

[Play Log: The Battle of Kawanakajima (Takeda Shingen)]

■ Player Information
- Player Name: your_name_here
- Faction: Takeda Clan (Takeda Shingen)
- Initial Base: Tsutsujigasaki Residence (Kai Province)
- Retainers: Yamagata Masakage, Baba Nobuharu, Naitō Masatoyo,
             Kōsaka Masanobu, Sanada Yukitaka
- Initial Troops: 20,000

■ Scenario Information
- Title: The Battle of Kawanakajima
- Year: 1561
- Initial State: Facing the Uesugi army, on the eve of decisive battle
- Enemy Faction: Uesugi Clan (18,000 troops)

▶️ How to Start the Game (IMPORTANT)

After pasting the template, you must explicitly start the game.

Paste the following immediately after the template:

Please start the game with this scenario.
You are the Game Master (GM).
I will choose actions as Takeda Shingen.

Describe the current situation first,
then present available actions.

🤔 What Happens Next?

The AI interprets the template as follows:

• You = the player (a nation / faction)
• AI = the Game Master (GM)
• Current state = 1561, the night before the decisive battle

In other words, the AI will respond like:

“You are Takeda Shingen.
The armies face each other at Kawanakajima.
What will you do next?”

And the game begins.

▶️ How to Play

The AI will describe the situation and propose options such as:

• Execute the Woodpecker Strategy (Kitsutsuki-senpō)
• Launch a night raid
• Prioritize reconnaissance
• Withdraw temporarily and reorganize

You respond freely, for example:

Assign the detached force to Yamamoto Kansuke
and deploy before dawn.

→ The game state updates and progresses

🔍 Why This Works

① Structured Natural Language = State Machine

• Player definition
• Initial state
• Enemy faction

This is effectively a finite state machine (FSM) written in natural language.

② Delegate the Hard Parts to AI

• Situation understanding
• Branch generation
• Narrative development
• Outcome resolution

All the parts that would be painful to implement in code
are handled entirely by the AI.

📐 This Is Not an “Article” — It’s a Game Definition

This template is:

• A novel ❌
• World-building notes ❌
• Game code ❌

👉 It is a game engine definition written in natural language.

That’s why it works immediately with:

• ChatGPT
• Claude
• Gemini

Just paste and play.

🏯 The Rekiden Experiment

Rekiden is an experiment in:

“History × Simulation × AI”

built with the minimum possible structure.

• No GUI
• No rulebook
• No implementation

There is only one template.

🔧 Possible Extensions

This design is easy to extend:

• Define explicit victory conditions
• Let AI handle probability (dice-style resolution)
• Run the Uesugi clan with another AI in parallel
• Turn it into multiplayer

✍️ Closing

The assumption that
“games must be built with code”
is rewritten for the AI era.

This template is the smallest possible implementation of that idea.

If you’re curious,
paste it into an AI and fight Kawanakajima yourself.

(To be continued: Rekiden Scenario Design)