The two of them were happy. Not a single doubt clouded their days. At least, until they decided to get engaged. The protagonist, Yu Takahashi, had only one lingering worry:
his fiancée Nanako Ukai's complete inability to hold her liquor. She loved to drink despite being a lightweight.

If that were all, it wouldn't have been an issue,
but whenever she got drunk, she would completely black out, losing all memory of what happened. Of course, both of them were well aware of this and took every precaution,
and their friends from college always kept a watchful eye on her at parties to make sure no "mistakes" were ever made. Some time after deciding on marriage... an anonymous letter arrives for him. "Your fiancée is cheating on you.

Behind your back, she's being plied with drinks and used however they please. Lately, she's even started faking drunkenness just to enjoy herself with other men. Are you still going to marry her?"
Though he initially tries to laugh it off, looking back, one or two uncomfortable memories begin to surface. It can't be... No, that's impossible...

But what if... This is a sensual tale of a man and a woman whose love for one another led them irrevocably astray.