Oh, the wake up scene - you need to have 100 relationship with her and seen previous events
If I understood correctly, you referred to the scene where you actually sleep with Yuna, then in the morning you both wake up and have sex - to get this scene you need to have seen all previous events (rel 20 cooking, rel40 running, rel60 couch fun, rel80 public bathroom blowjob) and when you reach rel100 and go into her room at night it should start