Two childhood friends, Eunchae and Jiho, decide to hit each other with a backscratcher to beat away bad luck. And why not? Nothing weird about a couple guys doing favors for each other — you scratch my back and I scratch yours! But sometimes it takes a hard hit to knock some sense into you... or some feelings into your body. Some very good feelings. As their bodies suddenly react to each new bump in their relationship, will their hearts also be tied together? For good luck, knock on wood!