Interesting twist that it's the same car.
I noticed in the flashback chapter - when he was a kid - that the car he was so fascinated by and then almost hit by was the same sort of car. But that just implied that he really liked that sort of car, so that's why he later bought one.
But apparently it's literally the same car.
And there's still a question of when specifically Chiaki was hit and killed. There was a scene of Kouhei talking to her after he recovered, after she saved him, so the implication was that it was a separate accident, later, when she was killed. But it's possible that she was killed when she saved him, and he suppressed the memory. That then would be how and when he saw her body, and the scene after he recovered was just the first time he talked to her ghost.
Lots of questions left, but it seems like we're making progress. Especially with the cop siding with the little sister - that should lead to some significant revelations.