Young has a full day: a fun morning at the comic book store with Violet and her son and then a lunch date with Christine, So Young and So Young's mom. In spite of her imposing presence, Young's mother-in-law surprises everyone at the table by thanking him for being a good husband to her daughter. Later that night at the bar, the cast breaks last season's record with an epic mega-Seoul Train. Tipsy, Steve makes a move on Christine - pissing off the overprotective Jasmine.
Annoyed about Steve making out with her sister Christine, Jasmine directs her anger at her BFF Scarlet for getting into her business. A string of conflicts is set off and reveals the ongoing beef between Scarlet and Violet. The next day, Jasmine brings the girls to the gun range to fire off some rounds as a hangover cure. Scarlet and Jasmine go out for some dim sum while the guys enjoy a round of beer bong and Korean BBQ. Steve starts seeing red when Christine and Jowe begin flirting with each other.
The cast heads to Busby's for Young's second bachelor party only to find the club empty. Despite Steve's screw up, everyone makes the most of it and still has a blast. Steve and Jowe attempt to hit on some girls at the bar while Scarlet surprises So Young with a lap dance she won't forget. Everyone's fun is cut short when Joe's girlfriend Jessica picks a fight with Steve and then Jowe and then Violet, which quickly escalates into an all-out brawl on the dance floor.
After being pulled out of a cat fight with Violet, Jessica gives Joe an ultimatum - he has to either choose her or his friendship with Jowe - but Joe is unable to give her a straight answer. Their intense arguing lights a fire to the tensions within the cast. Steve attempts to salvage Young's bachelor party until Jasmine accuses him of kissing another girl at the bar behind Christine's back. Frustrated at his friends' inability to get along, Young threatens to walk out and cancel the wedding.
For Young's sake, the cast manages to pull themselves from the chaos of the previous night and hash things out. The next day, everyone meets up at the Koreatown Plaza to make some last minute errand runs for the wedding. While shopping for Young's gift, Joe surprises the guys when he confesses he still thinks Jessica is "the one" despite their very public fight. However, the pressure of the wedding duties unravel the group once again as Steve forgets a key ingredient for the bar, Christine can't find the flower shop, and Joe screws up one of the most important ...
The season finale. Young and So Young's American wedding is a beautiful and tear-jerking send-off for their new life in Guam. That is until Steve nervously delivers his best man's speech. But his flub is quickly forgotten when he ruins Joe's big surprise at the ceremony after, making it the show's most outrageous episode yet. With special guest appearances from AMERICAN IDOL singer Andrew Garcia and comedian Paul "PK" Kim.