Kemumaki is a sleeping beauty (Ninja sleeping technique) (ケムマキ氏は眠り姫でござるの巻) is episode 598 of the Ninja Hattori-kun 1981 anime.
Kemumaki pretends to fall into a deep sleep, so Hattori sends Kenichi to the Koga Valley to get some herbs for Kemumaki. Fortunately, Hattori realises the prank at the right time - Kenichi is to go on a picnic with Yumeko, and because Kenichi has gone to the Koga Valley, Kemumaki will join Yumeko on the picnic. So Hattori disguises as Yumeko and feigns death.
It all starts when Hattori and the gang go to Kemumaki's flat. There they find a distraught Kagechiyo, who says that Kemumaki has been in a sleep-induced coma for two days now. Hattori then tries to knock Kemumaki over the head, which, sadly, doesn't work. He then tries to shout into a megaphone, only alarming everyone in the room (except for Hattori and Kemumaki). He then hears of a herb in the Koga valley. However, Iga ninjas aren't allowed inside, so the only person who can enter is Kenichi, which, unfortunately, means that he will miss the picnic that he and Yumeko Kawai were to go on. Kenichi's heart sinks - but he goes. Hattori and his allies are about to go too, but just then, Hattori hears a voice: Kemumaki has woken up, and says that Kenichi will be stuck in Koga Valley, so he and Yumeko will be able to go in peace. Hattori overhears, and tells the gang. Kenichi, who hasn't left yet, is outraged.
Next morning, Hattori goes to the picnic spot, disguised as Yumeko. When Kemumaki arrives, Hattori. collapses and feigns death. Kemumaki mourns the death of the fake Yumeko, just as the real Yumeko turns up with Kenichi at her heels. Kemumaki joins them on the picnic, just as Hattori celebrates his triumph.