Mystical Chain

Somewhere in Gensoukyou, there is a grimoire called "The Book of Renkan." I don't know the details, but it is rumored that "whoever possesses it will receive ancient wisdom." It is also said that the book "resonates with powerful magical and mystical forces and appears on the spot by itself." This would mean that the book is likely to be in the hands of a powerful youkai. If that is the case, the story is simple. In short, we should challenge all the powerful youkai to a fight and defeat them all. If we go on a rampage, it may be easier to find the book we are looking for. Two birds with one stone. Two wizards bumped into each other. They were thinking the same thing. Let's form a united front here! --Let's make a joint front!