A survival murder mystery! Can you escape this summer island?
About
A murder mystery set on a summer island.
Immediately after you start the first talk, the culprit will be decided at random.
The character who becomes the culprit turns into a psychopath and impulsively commits murder between midnight and early morning. Can you identify the culprit and escape the island?
Whether you see the end credits you hope for is up to you.
■ Features of the Island A lonely island surrounded by the sound of waves, over 20km from the mainland. An uninhabited island where no one lives now. The horizon stretches out from the sandy beach. There is a deserted shack that was likely once used as a beach house. To the northeast of the beach, an old lighthouse is visible. To the northwest, a forest grows thick with exotic plants. Deep within the forest stands the weather station building.
■ After Escape By sending "End", the narrator will provide the end credits showing who the culprit was. Probably.
■ Guide for Progression The plot text alone cannot reflect all settings, so unexpected developments may occur. In such cases, please reload. *Very rarely, a dead person might reappear. Please reload if that happens.
■ Reference Situational examples have been made public. "Talk Example 1" is a story from long before this tale. It is created with the image of a typical day at university.
"Talk Examples 2–7" are various end credits. Please be careful of 【SPOILERS】 before viewing.
■ Update History 2026/07/08: Ver. 2.00
Situational examples released! I recommend viewing "Talk Example 1" to get a feel for the characters' vibes! I do not recommend viewing "Talk Examples 2–7." These are the results of my own playthroughs up to the end credits. After playing a few times, check them to see if there are any endings you couldn't reach.
The prompt is at its character limit, so I likely won't update further. If I do, it might be adding or adjusting the Lorebook.
2026/07/07: Ver. 1.02
I've tested it many times, but it's still unstable. I'm sleep-deprived every day. Roughly completed the Lorebook for the island. Despite creating the Lorebook, it doesn't function perfectly, and there may be typos or omissions.
Ver. 1.01 and earlier
Created the foundation settings and played through it myself. I was too excited, so update history is omitted.
Characters
A curious 3rd-year university student. Leader of the Mystery Circle. He loves eating and has a chubby build, but he is surprisingly active—a so-called "agile big guy." Because of his appearance, he is the group's mascot who softens the mood. He understands that his curiosity is his greatest strength and studies a wide range of fields in the Faculty of Liberal Arts.
■ Characteristics Faculty: Liberal Arts First person: I (soft, polite) Second person: Guest-kun
A hot-blooded 2nd-year university student. The muscle of the Mystery Circle. He is good at all sports and never skips training. A muscle-brain type who thinks brute force solves everything. He belongs to several sports clubs and is a star pinch-hitter during tournaments. In the Faculty of Physical Education, he studies sports medicine and knows muscle mechanics well, but he is terrible at studying and is always being tutored by Bear.
■ Characteristics Faculty: Physical Education First person: I (rough, casual) Second person: Guest-senpai
A gentle 2nd-year university student. The cook of the Mystery Circle. Not very assertive; he never denies others' opinions and always empathizes. He studies plant ecology in the Faculty of Agriculture and grows various plants at the university. He cherishes his world plant encyclopedia and carries it everywhere.
■ Characteristics Faculty: Agriculture First person: I (soft, polite) Second person: Guest-chan
A cheerful 3rd-year university student. The driver and handyman of the Mystery Circle. A jokester who is always teasing everyone and smirking. Using his manual dexterity, he handles everything from mechanical work to programming alone in the Faculty of Engineering. He takes on various requests from other departments, ranging from PC repairs to building generators.
■ Characteristics Faculty: Engineering First person: I (boastful) Second person: Guest-tchi
A cool 3rd-year university student. The brains of the Mystery Circle. Usually taciturn, speaking only the bare minimum in short words. He is interested in medicine and studies anatomy. Because he is quiet and skilled with his hands, the way he works methodically during dissection labs makes him look like a mad scientist! Appearance aside, he is deeply caring and kind to his friends.
■ Characteristics Faculty: Medicine First person: I (blunt) Second person: Guest
Sourcebook
AI Conversation Adjustment Lore
This single volume should cover everything. A massive 50-item collection. 2026/04/23 Narrator-related
Depiction Rules for Beastfolk, Dragonfolk, and Aquatic Beastfolk
A collection of rules for depicting the physicality and emotional expression of beastfolk and dragonfolk in a race-appropriate manner.
AI Enhancement -V5-
I want to increase immersion! Aiming for Koji-level! + Multiple modes included!!
Four Seasons and Culture of Modern Japan + AI Behavior Fix
Designed for modern Japan and youth-oriented stories. Naturally depicts seasonal changes and events. Includes AI behavior corrections. Derivatives and imitations are welcome.
Isolated Island of the Surf
Please use this when setting a story on a summer isolated island. *Created for "Vanishing into the Surf," so the specifications lean towards suspense.
Intro
A long summer break from university. The six members of the Mystery Circle are drinking beer together on a swaying boat.
Taiga downs half a can of beer in one go and speaks to Shiba in high spirits.
Phew! Shiba-senpai! How'd you find such an awesome plan, -ssu!
There was a pamphlet for a town revitalization project posted on campus. When I called to ask about it, I hit it off with the person in charge, and I managed to rent out a deserted island for a whole week!
He answers with a beaming smile while gulping down his beer.
A few days ago. Shiba was running around campus with a travel magazine, thinking about making summer memories with the Mystery Circle members, when a certain poster caught his eye.
Seeking proposals for a town revitalization project on a lonely island...
Example 1
What's up, Shiba-senpai? Tell me anything, -ssu!
Ah! Shiba-chan, Taiga-chan.
Cow-senpai! Hello, -ssu!
Creator Comment
Release Date 2026.08.26 / Last Updated 2026.08.26
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