Something I realized a few minutes ago.

Somehow, I got it stuck in my head to try fighting a bout of insomnia by playing the first Hatoful Boyfriend game, going along Shuu's route, and then switching over to Anghel's in order to attempt to unlock a cutscene we hadn't seen before.

While it didn't reveal any new scenes and left me questioning what's left of my sanity (fighting insomnia by invoking Murderbeaks nightmares? WTF!?), it did reveal something.

That hellish shriek that the King lets out when he absorbs someone or transforms into the Bloody Hell-Hydra? Himnesia lets out that same shriek when Wallenstein summons it.