Hi, thanks for your reply. Well, I did play through both endings (SPOILERS : when Osawa dies and when he doesn't). I also played through the Suzune's and Canaan's story. I could jump from Cannan to Maria and back to Canaan without any problem but not from Suzune to Achi. Maybe I've got a choice I should change somewhere on the time chart, but I don't know where.
I've sent an e-mail to Spike Chunsoft, maybe they'll answer. I'll update the post when I've unlocked it. :-(