Two years ago Jin Kamishina survived a shuttle accident that killed the rest of his family, causing in him to live out the rest of his life alone. Meanwhile Earth faces possible destruction from an asteroid, and thus the ISDA works on "D-Project" to stop it. In a facility Kazuki Tachibana, Jin's old friend, is tested for his compatibility with a Dragon, which is a success. Elsewhere, Jin witnesses a strange creature almost kill a woman. The creature goes after and eventually catches up to him, causing Jin to fall out of a window. However, Jin is saved by a mysterious girl who is able to fight off the monster. When Jin wakes up, the girl introduces herself as Toa.