Seung-bum Ryoo

A former professional baseball player, Byeong-wu, made a successful career transition into a high-flying insurance advisor, thanks to his keen business sense and quick wits. But one day, one of his clients committed suicide and passed away and once hero Byeong-wu is now subject to internal investigation. Now he starts to run through his client list and finds a suspicious group of people introduced to him by the same person - and starts visiting them one by one.

Seemingly an ordinary math teacher in high school, Suk-go is indeed a brilliant mathematician. Hwa-sun is his neighbor. They become inseparable when Suk-go decides to cover up Hwa-sun's accidental murder while she was mercilessly beaten by her ex-husband.