This Korean drama was called School 2015. It was a very popular Korean drama about a group of students in a high school in Seoul. One of the teachers, Cui Zeyu, was a gangster in the neighborhood, but he was very passionate about education and planted a cherry blossom tree. With his help, the students in the class gradually became positive and learned to respect each other. The entire TV series was full of drama, romance, and camaraderie, and was deeply loved by the audience.