My Youth Romantic Comedy Is Wrong, as I Expected @ Comic Vol. 17 (manga)

During a break from helping to put together a prom for Soubu High School, Hachiman and Yui head to the hardware store to choose a gift for Komachi to celebrate getting into high school. While looking at possible gifts, the two of them...look an awful lot like a couple?! But the day after, Iroha abruptly makes a face and enters the classroom, her brief comment bringing dark clouds looming over the prom's opening...