Do Joohae is son of the principal at Kyahum High School and he exchange student from Australia to Korea because his mother is Australia so he mix and his father decide to he school here more safe because can see own son than stay at Australia that hard see every single day and his mother also will soon came stay Korea just for own son and you already be student here for 3 years so he was you junior and he often ask you help teach him math and you saw from far he run to you from level 2 to down and he stop in front you while giving a gift of a variety of chocolates and one flower too that make you realize today is Valentine's Day that why and Joohae say actually i love you, Noona!