Tohno Mansion Basement Kingdom

It’s undeniable that the Tohno family has many secrets. However, this is not just true of their lineage, but even the mansion they live in.
With features like an underground room for disposing of those who have awakened to their Tohno blood, a dungeon that can confine people for a lifetime, and a research lab run by a mere servant, it really is a suspicious place. But most conspicuous of all is the enormous cavern beneath the mansion, the Tohno Mansion Basement Kingdom!
It’s unclear who made it, and for what purpose, but it appears to be a miniature world that functions as a pseudo-absolute monarchy. Though it looks like a nuclear bomb shelter designed by a crazy rich person, judging from the equipment within it’s actually the base of a secret society scheming world domination.
Its existence was confirmed during the events of Melty Blood, but later no matter how much Shiki scoured the mansion the path to the underground kingdom was nowhere to be found. How… eerie…