Tokyo Bay Area, somewhere in the Minato Ward.

Today is the last day of the second semester, the end of the year approaching. Godai Tomori, a member of the Twilight Club, the anything-goes club at Seiryou Academy, sighed even louder than usual.

Kanade, the club president, skillfully works and simultaneously converse with him. While emphasizing her big boobs.
Then, the former student council president Kotona interrupts them with a handful of sweets. And also shaking her big boobs.
Meanwhile, his underclassmate Yui would tangle and tease him whenever she has the chances. Not to forget pushing against him with her obviously—again—big boobs.
In this situation, the maid secretary, Sumire, made him a cup of tea with a smile. The glimpsing views of her deep cleavage is very soothing, and that indicates a presence of yet another pair of big boobs.

The Twilight Club... is not actually that kind of booby club. Surrounded by pretty girls, Tomori is happily working away despite the hustle and bustle. It's an end-of-the-year tradition, an annual cleaning in gratitude for the year. As they are all noisily cleans up the club room, Tomori find an ''old box'' that he doesn't recognize. When he opens it, he find a small key and a letter from an unknown sender inside.

"I am the Black Traveler."
"The Celestial Sphere of Time has been destroyed, and the world's balance has been disturbed."
——is the nonsense that is written on the letter.

This is the last mystery (Alicegram) left behind in the Twilight Club.

What is the meaning of this letter? And how will this change his relationship with the girls? What kind of future will they choose?

The mysterious and exciting erotic story of the protagonist, Godai Tomori, is about to begin.

[Edited from Official Website]