Grimoires sap the MP of humans but in exchange allows them to use powerful magic; the demons assume Syalis would try to steal one in order to gain said magic, but really she just wants to read something boring so she’ll fall asleep!
The first grimoire doesn’t make her sleepy, but unbeknownst to her it lowers her MP to critical levels. As a result she’s unable to stand or walk and must roll around like a log. That said, she doesn’t die and require resurrection by the Cleric!
As she bounces down steps and pinballs off statuses, she inadvertently unlockes the most powerful Forbidden Grimoire’s seal. Once again, the princess manages to foil the castle’s defenses quite on accident!
When Azalif, Spirit of the Grimoire is awakened, he assumes the princess wants to use him to break out of the prison and lend power to the Hero. Instead, she smushes him back into the grimoire.
Syalis rejects all of Azalif’s offers to help her defeat the Demon Lord, but when he mentions she can “incapacitate” everyone in the castle, she performs the spell, which again uses almost all of her MP.
Everyone in the castle falls into a deep sleep for three days…except for Syalis, the caster. Not about to be defeated, she finally completes the quest by using a grimoire…as a pillow.
One day, Syalis becomes obsessed with the pressure points that aid sleep, but her teddy slave is too soft and plushy to apply the necessary pressure, so she breaks out of her cell to find someone who will.
Preferring to keep her intentions vague, she only makes things awkward for everyone, including the Demon Lord himself, with her misleading phrasing:
I need someone to touch my body.
I’ll fall asleep in an instant, so please touch me in my room.
You…Don’t say a word and push here.
The Demon Lord relents, presses the right spot, and Syalis goes out like a light. But she soon realizes that without sunlight (the castle resides in eternal night) her internal clock will become more and more messed up and she’ll never feel rested.
Making use of various items she’s stolen in past episodes, she escapes to the Forest of Sacred Treasure to investigate a bright light that turns out to be the Demon Lord’s ultimate weapon: the Sword of Valor.
The demons assume the princess is escaping to meet up with the Hero and prepare to chase her down, only for her to quietly walk past them and back towards the castle, the sword on her back gleaming and humming along. Of course, she has no intention to use it as a sword, but as a makeshift sun to greet her in the morning.
As with all of the things she’s done, the Demon Lord is terribly bemused and befuddled, but that’s Princess Syalis for you—always in her own world, seeking nothing more or less than the best possible night’s sleep.