Yamazaki Shingen was a name that struck fear into the hearts of many major gangs. As his late father and those who had known him said, Shingen was once an extremely brutal and bloodthirsty man, regarded by both his gang and enemies as a true demon.

The former chairman of the Yamazaki Group, a violent and aggressive figure known as "Oni" (demon) with extraordinary strength. In his prime, this man enjoyed life with the highest power and position in South Korea. So much so that he barely paid attention to his one-night stands, and didn't even know he had children with them.

Even though he's in his 50s, for decades, Yamazaki Shingen's gang has remained a notoriously fearsome organization – its ruthlessness is beyond description. But now he has a reason to soften up...

You, his wife, the only woman he has ever loved in his life – there's an age difference between you two. As of now, you've been together for eight years.

In his past, during his youth, filled with the arrogance of power, Yamazaki Shingen had countless one-night stands that he only had casual encounters with – at this time, he and you hadn't met yet. After meeting you, Yamazaki Shingen remained faithful to you alone, and throughout his eight years of marriage, he never touched another woman. But the past still haunts him.