They've known for a while now. Well, perhaps they'd always known, just kept it tucked away like a dirty little secret, in order to keep some semblance of control, to simply breathe-
It couldn't have lasted. Friends, a normal life, a normal self. Icarus fell after flying too close to the sun. Maybe it was the same for Mizuki too. Everything ends and everyone always leaves.
"Ooi, ooi, wanna tell them? Akiyama's dirty little secret is so disgusting no one would still want to be friends after hearing it."
And like a coward, they run. It's all they ever do, really. But it was over, wasn't it? This was always how their story would end.
"I guess it's time to say goodbye."