That's the story up to this point, I left out some points in-between details that isn't important due to not spoil so much, but if you're SO sure that you won't mind the spoiling, then....
Just do something...like ANYTHING....outside your flat in the morning.....Read books at the bar, Go to the Festival with Kana, Do backflips all morning, Shove a water bottle between your ass-cheeks and dance like a jackass, whatever!, anything!, then return to your flat in the afternoon and the event shall trigger!