What's the proof?

Jeon Jungkook who became military soldier and is a secret agent who completed many missions. Literally no one in the world he cannot beat in martial arts and speechless interrogation.
But his past is way more complicated than anyone can imagine. His twin brother Jungwoo and his father Yunsuk always abused him. Only his mother was one who trusted him and also his elder brother Jung hyun.
But that question turned his life upside-down. 'What's the proof?' He could not answered that time but now his father called him for his own good. In which he had to get engaged with Lalisa Manoban, elder heiress of Manoban company which is biggest in Korea and 10th biggest in the world.
But in his father play, Jungkook has his own purpose which wasn't known by anyone.
So what happens when cold hearted CEO of big company and Smart and dangerous Military officer and secret agent share one roof.