Love Rain depicts a 1970s pure love and a love from the present day... at the same time. It shows how the offspring of a previously ill-fated couple, who met in the 1970s, managed to meet and fall in love.
1970's In-Ha (Jang Keun-Suk) is a university student majoring in art. In-Ha and his friends Dong-Wook (Kim Shi-Hoo), a medical student, and Chang-Mo (Seo In-Guk), a law student, are popular at school, especially with women. In-Ha, Dong-Wook and Chang-Mo also enjoy playing the guitar and singing together. One day, In-Ha passes female student Yoon-Hee (Yoona) on campus. It takes no more than 3 seconds for In-Ha to fall in love with Yoon-Hee. He later sees Yoon-Hee sitting on a bench, while painting. In-Ha begins to paint her portrait, but the next moment she is gone. In-Ha runs out to find her and, in his excitement, bumps into Yoon-Hee. Yoon-Hee drops what she is holding. In-Ha helps to pick her stuff up, but doesn't say anything to her. After she leaves, In-Ha discovers a small notebook that she left behind. The notebook is her diary. At night, In-Ha opens up the diary and reads a page. He learns that Yoon-Hee's parents died and she loves the American film "Love Story." He then closes shut the diary. The next day, In-Ha waits for her outside a campus building to return her diary. When he turns around and is about leave, Yoon-Hee appears and asks In-Ha if he has seen her notebook. In-Ha doesn't speak up in time and misses returning her diary. In-Ha then reads more from her diary, this time from front to back multiple times. On a rainy day, In-Ha sees Yoon-Hee standing in front of building without an umbrella. In-Ha offers to walk her with his umbrella. As they walk together they feel a bond. A date is set to meet the following Sunday to watch the movie "Love Story". Later, Dong-Wook takes In-Ha and Chang-Mo to a get-together at a restaurant. Dong-Wook asks In-Ha and Chang-Mo to help him get closer to Yoon-Hee. Dong-Wook met Yoon-Hee the day before and also fell in love with her. She reminds him of his late mother. Because of this, Dong-Wook had asked his friend Hye-Jung (Son Eun-Seo) to bring Yoon-Hee to the get-together at the restaurant. With that brings in anger and despite.