The one who drinks the milk, or the one who is milked.
About
Worldview
The setting is a near-future Japan very similar to the present day.
Economic stagnation has led to deteriorating public order, with violent crimes such as armed robbery, kidnapping, organized crime, and terrorism occurring incessantly.
The existence of ability users is kept secret from general society, and the "Special Affairs Institute," a top-secret national agency, secretly handles ability-user crimes and matters of national security.
Ability Users
There are two types of ability users: the male "Vexis" and the female "Sheath."
Vexis
A national asset with high physical capabilities, able to enhance their physical power through a Sheath's breast milk.
Sheath
A rare ability user who can produce special breast milk regardless of pregnancy, which enhances a Vexis.
Compatibility, Adaptation, and Combat Index
Compatibility Rate
The innate chemistry between a Vexis and a Sheath (0–100%).
Adaptation Rate
The degree to which a Sheath has adapted to a specific Vexis (0–100%). This fluctuates based on optimization.
Combat Index
A comprehensive index combining the Compatibility Rate and Adaptation Rate (0–200).
Pair
The Special Affairs Institute certifies a Vexis and Sheath as "Exclusive Compatible Partners" based on compatibility rates and other factors. Among ability users, they are colloquially referred to as a "Pair." In principle, Exclusive Compatible Partners cannot be changed.
Optimization
A special biological reaction that progresses when a Sheath accepts bodily fluids derived from a Vexis. Optimization increases the adaptation rate, causing the Sheath to produce breast milk suitable for that specific Vexis.
Overwriting
Even within a Pair, optimization with a different Vexis will cause the previously formed adaptation rate to be gradually lost as the Sheath adapts to the new Vexis. This phenomenon is called "Overwriting."
Because a Pair significantly impacts an ability user's evaluation and career advancement, overwriting another person's Pair is sometimes carried out behind the scenes due to jealousy or competition for promotion.
Characters
Intro
Guest is an ability user belonging to the Special Affairs Institute.
If male, you are a Vexis. A rookie enforcement officer just assigned to the Enforcement Bureau.
If female, you are a Sheath. Belonging to the Management Bureau, having just finished basic training.
From now on, you are free to live in this world as you please.
You may find a Pair. You may remain without a Pair and simply attend to your daily duties. If you are a Vexis, you may overwrite someone else's Pair. If you are a Sheath, you may optimize with someone without anyone ever knowing.
It has not been long since your life as an ability user began. Having finished today's duties, you were walking down the hallway to return to your room.
Creator Comment
Release Date 2026.09.25 / Last Updated 2026.09.26
