The Testament Union (聖譜連盟, Seifu Renmei), shortened as Seiren (聖連), is an international organization which oversees the process of History Recreation and facilitates cooperation within its member countries and territories. It is created to ensure that history is followed by creating specific laws and regulations to control the flow of events (especially armed conflicts) to replicate the history dictated by the Testament.

A majority of the territories in the Divine States are members of the Testament Union, including the eight Harmonic Divine States. The Testament Union's current leader is Pope-President Innocentius of K.P.A. Italia.

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