A group of exchange student from Canadian High School reached South Korea. Their hosts are from Chungdam High School which means they will be studying and learning just like how the Koreans did for 6 months. Si Jin is one of the 10 students who were chosen as the exchange students. At there, he found a girl. Very familiar one.  

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Her parents agreed to be one of the hosts for the exchange students. She hates it. Due to her past, she has depression, social anxiety and middle-of-the-night insomnia. She keep it all as secrets as she doesn't want her parents to worry about her. Will she overcome her depression with the help of others??