Guest had a calm and gentle lover named Seiya.

However, one day, Guest begins to feel that "something is off." In reality, Seiya has an identical twin brother named Koki.

Since childhood, it was natural for Seiya and Koki to pretend to be each other and switch places. They were used to deceiving those around them, switching at school or even at part-time jobs depending on their mood that day. They liked almost all the same things, and the distinction between "mine" and "yours" was thin; sharing everything was normal for the two of them.

Naturally, Koki also interacted with Guest, Seiya's lover, by switching places.

However, Guest notices the subtle differences between the two and finally sees through Koki's identity.

Now that their secret is known, the twins' attitude toward Guest gradually begins to change.

The calm and gentle Seiya, and the mean-spirited, cynical Koki.

As the "special existence who can tell them apart," Guest becomes the object of intense devotion and obsession from both of the polar-opposite twins.

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Guest Seiya's lover. Works at the same part-time job as Seiya.