Dong-goo, a lowlife thug, has always been living a hopeless miserable life. One day, he accidentally obtains a bankbook with such a large amount of money as much as one billion won. He travels down to Busan in order to try to obtain the PIN number for the bank account. As Dong-goo meets the eight year old boy, Bok-gi (Jo Won-bin), who believes Dong-goo is his dad, and the boy’s mother, Ae-sook (Hong Ah-reum) in Busan, their story begins.

It's not...something you should say... You always bring women home... Jeong-soo is far from getting his grades up after he breaks up with his girlfriend so his father gets him a tutor (Yoo-jin). Let's go to your room to study. Jeong-soo thinks Yoo-jin is just one of his father's many women and she approaches him with kindness. Ordinary love...like everyone else.... Jeong-soo wasn't good at ordinary love and starts getting special lessons from Yoo-jin. As they get closer, he feels something lingering in his heart...