The sasumata (spear fork) is a polearm 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.
This tag implicates polearm (learn more).
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