As you all know, your Good Friend Devil Man is an ABSOLUTE STUD!

And he experiences insomnia when he is in bed with a Beautiful Goddess who wants to make mad PASSIONATE love to him all night long, for a Night with Devil Man is a truly Heavenly Night with must be Cherished For the Rest of Eternity

Ergo...

The Beautiful Goddess enjoys every single PRECIOUS minute of her time with Devil Man, for Devil Man is a TRULY AMAZING MAN

Which means Devil Man gets no sleep at all

Thus...

Insomnia!

But when Devil Man is in bed alone, he sleeps soundly and peacefully