Hatena Illusion

On the night of his 30th birthday, one man’s dreams of wielding magic come true after he unexpectedly passes away. He wakes as Sion, a young child in another world. He and his elder sister, Marie, are the children of a lower-class noble family who govern their region. After receiving conflicting messages from their father, Sion and Marie set out on an adventure to uncover the magic.

When young Princess Syalis is kidnapped and imprisoned by the Demon King, she's rather indifferent about her situation. But she quickly comes to a terrible realisation—she can't sleep soundly in such an uncomfortable bed! She soon escapes her cell and sets off in search of ways to improve her sleep quality, leaving the castle's inhabitants, and even the Demon King himself, scrambling to keep the unruly princess out of trouble during her chaotic adventures.

Rather than take a more sensible approach to salvaging his grades in time for graduation, Alto summons a bit of otherworldly help. Only after does he learn he’s bound the legendary she-devil Vermeil into service as his familiar!

Akira is a normal high school boy, but he nevertheless impulsively licks some drool left by the mysterious transfer student Mikoto. The next day he falls asleep with an inexplicable fever. After five days Mikoto suddenly comes to visit, and makes him consume her drool. The fever instantly vanishes, and Mikoto explains that he's suffering from "love sickness." She can transmit emotions through her drool, and the two of them are now bound together.