I assume you didn't get for example Goushikisaka-hen (Multicoloured Burial Mound Book) (it consits of I think 3 individual chapters)?
Try not going with the girls to the cake-shop at the second day of school.
Later when you push Mana up a hill, try going straight ahead, without searching for a detour, you will end up at Kaori's home.
The end is a bit...different for, for example The chapter of the Duet Rebirth (Sousourinne no Shou). I think all of them somehow involve Kaori's story.