Ah okay... the bit about Ryo committing suicide happens after this part. The prologue was kind of like a "letter" from Yamapi to Koyama, asking for explanations of what had happened between Ryo and Shige. So now we're going back in time to see what happened to the four of them...with a bit of time jumping here and there :) Pretty much right now, the story stands at Koyama and Yamapi getting together.