Shoehorning in that annoying ass character was NOT the only way the author could have written this, Oomori could have gotten confessed to by someone else making Yuu realize he needs to stop dragging his feet, or Itoko, knowing his "trauma" could have set up a scenario that would help him gain...
See, it's one thing if they were just a bit nicer because that's normal, but they actually sidestepped their kids and said they'd rather trade them in for their friend like it's some fantasy football team ☠️☠️☠️