Nemureru Mori no Rega

Deep within a dark, dark forest, there was a princess who had been put into a deep sleep by an evil dragon. To save her, Rega, the captain of a kingdom's knights, challenged the evil dragon to battle. The dragon's power was immense, but with his feelings for the princess in his heart, he somehow managed to defeat it. Reunited with the awakened princess, Rega's heart overflowed with joy. And then, the princess said to him: "Be cursed." Now begins the adventure tied to this tale. (Source: Kodansha, translated)