Baek Sijin is assigned to the F12 Center as a diagnostic examiner, where his lifesaver, Esper Ham Geonwoo, also works. Feeling both nervous and excited, Sijin heads to work, only to find an unexpected obstacle waiting to challenge him. “If you’re really not interested in Ham Geonwoo, then there’s no need to be so uneasy around me. Am I right?” The obstacle turns out to be Jeong Taeyul, an A-rank Guide highly compatible with Ham Geonwoo. Taeyul clings to Sijin, constantly meddling and trying to keep him in line. Despite finding him irritating, Sijin can’t help but notice Taeyul more than he wants to, especially when poor test results trigger his sense of duty. Could this tension lead to something unexpected?