The Spirit Realm

Due to his fatigue, Nakao Ryuu slept on his table in his office. When he woke up, he was suddenly in another realm called "Spirit Realm". What's more is when he was sleeping, he can go back and forth from Earth and Spirit Realm. While staying at the Spirit Realm, he was asked by the spirits to protect the Spirit Realm against the Dark Devils, who was lurking around the Outside Realm. Can Ryuu protect the Spirit Realm while going back and forth from Earth?