Tsukishiro Haru was born with a peculiar constitution: he gets intoxicated by caffeine. He's an ordinary high school student with a slightly unusual body, who until now has never had a girlfriend.

So, he made sure to avoid caffeine-containing drinks as much as possible. However, a junior who was unaware of his constitution bought him coffee, and after drinking it... he became intoxicated and promptly lost consciousness.

And when he awoke...

"We're dating on the premise of marriage... Haru-senpai. You promised, didn't you!"

His junior had become his fiancée.

No, and not just his junior.

"...because I 'promised' I'd marry Haru."

"Haru and I are bound by fate!"

And astonishingly, his childhood friends had also skipped past the lover stage and become his fiancées...!

But because he was intoxicated, he has no recollection of having 'made' these fiancées...!

Moreover, all three of them each believe they are his *sole* fiancée...!

No matter how he struggles, it's a lover's quarrel from hell!

A turbulent yandere rom-com begins!!