Accidental Miracle

Takemichi finds out about the baby three days after waking from his coma, a coma its father - its other father - puts him in the hospital with.

The doctors, in fact, find out much earlier; but Takemichi himself is unconscious with a vast amount of blood loss, he's lost his consciousness in pain and then lost in a drugged state of whatever pain medication he's constantly pumped with, and so, even if they tell him, he doesn't remember.