hmmm... if this is turning into a fanfic thread...
Aachan actually died before the season started (probably a knife stab wound), trying to save a small girl from a bunch of thugs.
Eating sakura petals to chain herself to Earth, she turned into a "black angel" of sorts and tried to stop these thugs throughout the story.
During the gang brawl, she appears in a ray of light.
Everyone stops, and many fall to their knees crying understanding the truth. The season has changed, and there are no more petals.
Shibuya is the most emotionally hurt, realizing she started a war against a school she loved just because she didn't want to be alone.
She calls the fight off and the groups disperse.
34min grad scene.