The story of this season still revolves around the five protagonists. Matthew (Jason Segel) and Lily (Alyson Hannigan), who have been in love for 9 years, finally decided to get married. When they were busy preparing for the wedding, the bride-to-be Lily suddenly went to San Francisco to study art without saying a word, so Matthew had to cancel the wedding. Three months later, Lily returned to New York and wanted to reconcile with Matthew. Will the heartbroken Matthew forgive Lily? On the other hand, Ted (Josh Radnor) and Robin (Cobie Smulders), who have a good impression of each other, finally understand their true feelings after various events and twists and turns, so they decide to be together. Playboy Barney (Neil Patrick Harris) still enjoys his bachelor life, but he remains mysterious in other aspects. Ted and the other four found that they didn't actually know Barney, so they all began to be curious about Barney.