Oh Seungpyo has always been at the top of his class, but once he enters high school, his spot gets stolen by Ryu Jaemin. No matter how hard Seungpyo tries, he can't seem to reclaim his place and is stuck in second. For the first time in his life, he develops an inferiority complex and, without realizing it, he starts keeping an eye on Jaemin. One rainy day, the two accidentally swap phones. Though it seemed like a minor accident, what Seungpyo discovers on Jaemin's phone leaves him in shock, complicating their relationship beyond expectation.