Kip. 12: My Teen Romantic Comedy is Wrong, as I Expected.

12

Hachiman and Yukino meet to plan a joint prom with other schools, but are short on time, manpower, and budget. They visit a potential location for the Prom, and he misunderstands her comment when they see a wedding. The next day more people than expected show up to help out, and later the boys take a break relaxing at a sauna. While they're preparing the ballroom, Komachi shows up and Iroha gives romantic advice to Yui. After the event, Hachiman and Yukino wrap things up and she leaves him speechless with a confession. While dealing with the aftermath of the joint-prom, Komachi and Iroha come by to resucitate the 'Service Club', then Yui has a request. (Source: Wikipedia)