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The Kuroba (黒羽, くろば, lit. black feather) Family is a Branch Family of the Yotsuba Clan.
They are the branch family responsible for the supervision and gathering of intelligence for the Yotsuba. 
Kuroba Fumiya, the eldest son of the Kuroba had been the number two candidate in-line for succession of the Yotsuba Clan.  That is however before he relinquished that position in favor of his cousin Shiba Miyuki, for which his entire family was in agreement. 
All of the agents the Kuroba employ, use 'Poisoned Bees' as their trump card; a Sensory Systematic Type Magic that increases a target’s pain perception infinitely until death. The greatest advantage to “Poisoned Bees” is its ability to finish an opponent with the tiny prick of a pin, leaving behind a nondescript wound that would be hard to link as the cause of death. 
Yotsuba Maya had made the Kuroba disseminate information about themselves in order to start a rumor.  Then during the AD 2096 Nine Schools Competition, the rumor going around since Spring that the Kuroba had spread, was that they were a Branch Family of the Yotsuba. This is mentioned by Yoshida Mikihiko to Tatsuya. 
Near the Yotsuba Main House, there is a complex where the Kuroba Twins' grandmother, Yotsuba Yume, the little sister of Tatsuya and Miyuki’s deceased grandfather, Yotsuba Genzou, as well as aunt to the current family head, Maya lives. 
Area of Influence
- Kuroba Juuzou (黒羽 重蔵) - (Former House Head, Deceased)
- Yotsuba Yume (四葉 夢女)
- Kuroba Ayako (黒羽 亜夜子)
- Kuroba Fumiya (黒羽 文弥) - (Forrmer Candidate - Withdrew Before Announcement of Heir)
- As with all of the Yotsuba Branch Families, the family name is either derived from a variation of Yotsuba, or the name of a flower having four leaves.