sasumata
The sasumata (spear fork) is a pole weapon used by the samurai class and their retainers in feudal Japan. It was used as a policing tool used to arrest people, with the forked end used to capture a person's neck or limb.
It's Eosinophil from Hataraku Saibou's weapon of choice. They are also commonly used by the characters of Chiikawa.