Prince Asta -- the last surviving member of a royal family -- must fulfill a quest before he can claim the throne: find the legendary "Key to the Kingdom." Thanks to the clever manipulation of Gaius the Dragon Man, Leticia is witness to a conversation in which her bodyguard Alex declares his love for the beautiful Latona. Traumatized by this revelation, Leticia foolishly puts herself and Alex in harm"s way. Meanwhile, Asta finds the first of the Invisible Towers, said to hold crucial information about the "Key." The shocking secret he unearths be must shared with the other participants in the quest, but his way is blocked -- first by the elements, and then by a Dragon Man!