Jisung, a curious and observant young man, discovers that his neighbor from apartment 143 is being cheated on. Lacking the courage to confront him directly, Jisung attempts to warn him subtly by changing the name of his Wi-Fi network to "Neighbor in Apt 143, Your BF Is Cheating on You." However, when he realizes that his tactic isn't working and the infidelity continues, Jisung is forced to face his fears. He ultimately decides to speak to his neighbor in person, grappling with the dilemma of revealing the truth or continuing to silently watch from the sidelines.