Park Yun Jae is a university student studying astronomy. He met Kim Ji Eun on his first blind date while attending university. They fell in love and became boyfriend and girlfriend. One day, a strange man appears in front of Yun Jae and tells him that he is Ji Eun. Ji Eun is a pretty and warm-hearted woman. One day, she wakes up and finds herself changed to a man. She explains the situation to her boyfriend, Park Yun Jae. She begins to use the name Kim Ji Hun and learns how to live as a man from Yun Jae. The two decide not to break up and to wait for her to return to her original female appearance to continue their relationship. They try to figure out a way to make that happen.
Yoon Jae and Ji Eun, a couple from Yeonhee University, plan to go on a two-day trip together. However, just before the trip, Ji Eun turns into a good-looking man. Ji Eun and Ji Hye try desperately to hide this fact from Yoon Jae by pretending to be sick while Ji Eun contemplates whether to tell her boyfriend the truth or not.
While Yoon Jae struggles to love Ji Eun the same with her masculine looks, Yu Ri and Ji Eun discuss tactics to keep the relationship going. Meanwhile, Yoon Jae’s sister, Yoon Ah, falls for Ji Eun’s new appearance and Yoon Jae’s junior, Min Hyuk, becomes acquainted with Ji Eun’s new male self, pushing Ji Eun to come up with a temporary alter ego, Kim Ji Hoon.
Suddenly, Ji Hoon is back to looking like Ji Eun, relieving Yoon Jae. At the same time, Kang Min Joo, a junior of Yoon Jae’s, comes back to Korea from her studies abroad and invites Yoon Jae to a welcome-back party, irking Ji Eun. While Ji Eun plans to go to the party with her boyfriend to keep an eye on Min Joo, she faces an unexpected crisis.
Ji Eun and Ji Hye visit their parents, who believe Ji Hoon is Ji Hye’s boyfriend, in order to tell them the truth about Ji Hoon. Meanwhile, Ji Eun invites Yoon Jae, Min Hyuk, and Yu Ri over to make up for the drunken trouble Yoon Jae caused. While Yu Ri tries hard not to fall for her friend’s new looks, Min Joo begins to disrupt Ji Eun and Yoon Jae’s relationship in earnest.
The love triangle between Yoon Jae, Ji Hoon, and Min Joo deepens, and the competition to win over Yoon Jae’s heart begins in earnest. Meanwhile, Ji Hoon becomes Yoon Ah’s tutor, satisfying her need for handsome men. He also becomes Yu Ri’s knight in shining armor at her friend’s birthday party, causing an unforgettable scene for all.
Ji Hoon suddenly becomes a sensation on social media as Doe Eyes of Yeonhee University. To help Yoon Jae and Ji Hoon, Yu Ri decides to reveal her face and do a fan sign event. Ji Hye and her old school friend, Young Seok, finally meet properly and exchange numbers, and Yoon Jae is suspected of cheating on Ji Eun as he is seen coming out of a motel.
Park Yun Jae is a university student studying astronomy. He met Kim Ji Eun on his first blind date while attending university. They fell in love and became boyfriend and girlfriend. One day, a strange man appears in front of Yun Jae and tells him that he is Ji Eun. Ji Eun is a pretty and warm-hearted woman. One day, she wakes up and finds herself changed to a man. She explains the situation to her boyfriend, Park Yun Jae. She begins to use the name Kim Ji Hun and learns how to live as a man from Yun Jae. The two decide not to break up and to wait for her to return to her original female appearance to continue their relationship. They try to figure out a way to make that happen.
