Oak's not a fan of fog - his first night alone in the forest was during a fog. He was only a fawn, wondering lonely and frightened through the forest. He eventually found the pond and fell asleep. When he woke up, the sun was shinning and the forest was colourful and bright - and has been ever since until this morning. (Basically, apart from the night I first played on here, I've always seen beautiful sunshine XD.)
Oak headed for the old oak tree and waited there a bit. He went back to the pond and met a little fawn (in the final picture) and then came back to the tree and played with some of the other deer. Who were you guys? You helped Oak lose his fear of being alone in the fog. You're both on either side of Oak in the Final picture.
Sorry for taking up so much space XD.