• PLOT:

Year 2015, actually nothing changed except one little thing. Seong Bum (Yoo Seung Ho) is a experimenter he's smart, good looking but very poor. He dreams one day to develop a time machine to travel back, but fails multiply times and no company wants to buy his idea. As he almost gave up on his dreams he suddenly discovers a "Door" in middle of Seoul City, the strange thing is nobody can see it except himself. As he was slowly approaching the door to see if it's real, he couldn't believe what he saw.

Meanwhile Hong Se Mi (Sung Yu Ri) was adopted when she was 5, she doesn't know that she is a famous development companies grandchild, she lives the ordinary life, she studied business marketing and tries to find a job but also fails. One day a Driver came to her asking her if she was adopted, after her grandfather Hong Joon ( Lee Soon Jae) send her away after her parents loss. The Driver then asked Se Mi if her parents name were Hong Kyu Jin and Young Mi Na. Se Mi was surprised and agreed that they were indeed her parents. The driver then asked Se Mi if she was willing to meet her grandfather in the hospital who suddenly collapsed due to health problems.

Meanwhile the Company Stocks dropped.If there wouldn't have been more trouble Park Te-Oh(L/Kim Myungsoo) and his mother Park Jin Hee (Kim Sung Ryung).Jin Hee, Se Mi's step mom saw the chance to make her son Te-Oh the new chairman.

Apparently Te-Oh is not interested in leading the company he is an elite student hes spoiled and loves to drink& party. Of course his Mothers intention is to make him the successor of the Company. She doesn't like Se Mi, since she's not her biological daughter and shes a mistress. Everything goes wrong and the Company seems to get ruined.

Se-Mi went to the hospital to meet her grandfather were he was fighting against death, he then saw Se-Mi and finally could deliver the words he couldn't tell her in years that "she was indeed the last living successor" of the Company which is slowly falling apart.

Her Grandfather's last words were Hong Se Mi to safe his Company, while he closed his eyes. Hong Se Mi in tears just left. As she was walking towards the streets she saw a "Door" in middle of Seoul City, the strange thing is only she can see the door, as she got closer to the door she saw a guy standing next to it, Se Mi was wondering if he could see what she saw and indeed he did.

Seong Bum asked her if she could see the door and Se Mi said she does.Both asked each other if they could open the door together and as they opened the door they saw themselves a few years before.

Both get the chance to change the future in the past within 100days.

What do you think will happen to them? Will Hong Se Mi get the chance to safe the Company and will Seong Bum help her with his talent and ideas? Will he trust the company which took his dreams? Will they both fall in love with each other at the end?