Yasuo Teratani is Ichitaka Seto's friend, actively facilitating Ichitaka's romantic pursuits. He arranges social opportunities, including a Christmas Eve double date pairing Ichitaka with Iori Yoshizuki, and consistently encourages Ichitaka to confess his feelings to her. Yasuo meets Ichitaka, Iori, and Yuka Morisaki during the Christmas party, proceeding with them to a karaoke bar. He witnesses Ichitaka's initial drunken confession to Iori fail and the subsequent sober confession succeed. Yasuo then participates alongside Yuka Morisaki in efforts to reconcile misunderstandings between Ichitaka and Iori, including a specific failed attempt to facilitate their relationship. His consistent presence occurs solely within group settings centered on Ichitaka and Iori's evolving relationship, primarily appearing during coordinated social gatherings rather than individual subplots.