Etsuran Kinshi: Akatsukizuki Kyouju no Kaii Kenshou

A professor who loves horror and a woman who gets wrapped up in the shenanigans of it all investigate lewd supernatural phenomena?! Physicist Yukio Akatsuki's life work is all about investigating the supernatural. He has his editor, Kanade Tamamori, go to an inn that's rumored to be haunted by a zashiki-warashi as a part of his research...
(Source: MangaPlaza)