Mayonaka, Kare wa Betsu no Kao

I'm shy when it comes to love, and I'm known as the Ice Queen at work, but I'm engaged to the company's heir!? He's kind and sweet, and I had faith in our future together... but he has a secret I didn't know about...!!! My flawless fiancé changes completely at night... A mysterious love story!! (Source: Shogakukan, translated)