
I just finished the anime.. so which chapter should I read for the continuation? Or should I read it from 1st chap?

I recommend you to read it from the start (it's pretty much the same as in the anime, but it's worth the read!)
But if you want to read from where the anime left, you can start at chapter 24 which is the one where Ashiya gets his sight back (the anime takes a slight different turn to make a more "solid" ending)
Hope it helps!
He Tian