The story opens with a young man by the name of Severo, who lives on a small world a great distance from any others. However, it is attacked by the mysterious heartless, and destroyed outright. Lost in a void, Severo turns into the heartless Guard Armor, and after his defeat at the hands of Sora, he is returned to his 'true' form, albiet older and with different clothing, on another world- the Mushroom kingdom.
Having awakened, Severo searches the world for a short time, encountering Mario, who explains that he is on his way to Bowser's Castle to rescue Princess Peach. Severo acoompanies Mario, reaching Bowser's keep and defeating him as well as hundreds of Heartless and rescuing the princess. After the battle, Ivo has a short hallucination where he is forced to fight with a skeleton, which, after it's defeat, became a Keyblade for Severo to use (up to this point, he had been fighting with his fists.) Once the hallucination was over, the group returned to Peach's Castle.
When Severo awakened from his sleep, he found that he was no longer in the Mushroom kingdom, but in the mysterious land of Hyrule. How he got here and why is unknown.