This is a confidential file that collects unpublished letters from the time of the Seventh Great Demon King. But by chance, he was dug out from under the trash can by the Tenth Generation Demon King. A poignant history unfolds bit by bit... The brave, the knight, the noble, the princess... What kind of love and hatred happened between them back then? Let's open up these pieces of yellowed letter paper together and explore the mentality of those involved!