Cain finally reaches his twelfth birthday, the day he can register as an adventurer. He heads straight to the guild to sign up, but some older adventurers pick a fight with him, and he's saved by a red-haired man who looks very familiar...

Cain finds himself before Hirasawa Yuuya, the first king of Esfort. Yuuya tells Cain that the seal on the evil god Aaron is weakening, and Cain must fight him. Cain is hesitant, but then Yuuya tells him that Aaron is linked to Shiina Kazuya...