Yuzuru and Ibara constantly refer to each other as dogs and their bickering is recognised as a form of play by characters such as Eichi and Wataru. I imagined an AU in which Yuzubara are dogboys who behave like dogs and have body language like dogs so even when they're fighting they can't stop their tails from wagging in delight. Additionally, Ibara is a Dobermann Pinscher and Yuzuru is a Bull terrier, both of which are known to be aggressive towards other dogs.