Kimi wa Mendouna Konyakusha

The male lead is a handsome man with impeccable credentials who works hard but is also caring and kind (very important). The girl is beautiful, bright, straightforward, and charming. They meet at work and gradually develop feelings for each other, sometimes working together and sometimes clashing. Their attraction to each other soon leads to love. However, there is one big obstacle standing in their way. He already has a fiancée.

It's the ideal way to spice up a romance, a fiancée who acts… “troublesome”. That would be me.

(Source: Hakusensha, translated)