Plot is simple yet boring. One thing what i liked is 1st leads job. Different from all the dramas there. You will love his job, but drama is boring.

Two Oh's in same school. 1 beautiful and 2nd ok ok. 2nd girl is always looked down and compared to 1st. Later both goes separate ways. Fall in love with different guys.
beautiful Oh cancelled her marriage bcz guy's (1st lead) mom plays some trick. guy is unaware and thinks she cheated.
2nd oh is getting getting married happily. However 1st hero thinks this is cheater Oh (bcz of same name) and ruins 2nd leads business and he is about to go jail. 2nd lead cancels his marriage before the marriage day bcz of business but he says that he hates ok ok looking Oh.
Both 1st hero and Ok ok oh are in pain. Coincidentally they met and 1st hero understood his mistake.
2nd male lead released from jail and got to know that he was wronged from 1st hero. Later he starts pursuing ok ok Oh back but However OK OK Oh has fallen in love with 1st hero. This makes our 2nd lead angry.
Later you can think of story. both guys facing together and their cold wars, heartaches etc etc. I found it extremely boring. However finally 1st lead and ok ok Oh gets together.