Yep - glasses guy did it, and that's a lot of what this has all been about. I was pretty sure of that.
So has Chiaki manipulated Kouhei into this road trip for her purposes? Or is it something that Kouhei unconsciously did for her benefit? He does apparently have suppressed memories of her, so it's possible he's effectively tricked himself into helping her.
Odd twist that it's even the same car. I'm not sure what to make of that.