Ryou gets none of the development that she gets in the VN. Her development is the backbone of this entire arc. You do not get to see Ryou and Tomoya's relationship develop, you do not get to see Tomoya's feelings get more and more confused until they boil over and explode into a fantastic ending that was done so poorly in this adaptation, and you do not get to see the true extent of what Kyou was going through during this entire ordeal. Ryou is not meant to be the bad guy, but that is what I feel this adaptation was trying to do, and it is just so wrong.
I love the Kyou route in Clannad, but this adaptation did not even come close to doing it justice. The characters are undeveloped, the motivations make no sense, and the characters' actions are forced to say the least. I won't tell you to not watch it, but if you have the ability to, please play the VN before watching this OVA. It will be so much more satisfying.
