Two male teenagers, one of them is blond and the other is redheaded

Two male teenagers, one of them is blond and the other is redheaded. They are sitting inside a cave. They are only wearing swim trunks. They are kissing. Deep in the cave, there is a pile of gold coins and an awakened dragon. The dragon is very big and very beautiful. He is scarlet green with yellow and has very large wings.. He's on top of the treasure pile. Further ahead, you can see a lake. The image must be in anime.