Circle.
Japanese name: 介錯 (Kaishaku)
Members: 七戸輝正 (Shichinohe Terumasa) and 太田仁 (Ota Hitoshi)
Pixiv username: seven
Kaishaku is a two-member mangaka circle, most famous for their Kannazuki no Miko creation. The circle name comes from Kaishakunin, an appointed second person whose duty is to decapitate one who commits seppuku.
https://www.pixiv.net/users/838487
https://www.pixiv.net/stacc/k-seven
https://twitter.com/Kai_Seven_
https://twitter.com/intent/user?user_id=87707280
http://kaishaku0.blog.fc2.com
https://www.melonbooks.co.jp/circle/index.php?circle_id=17641
https://www.melonbooks.co.jp/circle/index.php?circle_id=54978
https://www.melonbooks.co.jp/circle/index.php?circle_id=62121
https://www.melonbooks.co.jp/search/search.php?mode=search&text_type=author&name=介錯
https://ec.toranoana.jp/tora_r/ec/app/catalog/list?searchActorName=介錯
https://ec.toranoana.jp/tora_r/ec/cot/circle/2UPAE36P8U7NdE6pd687/all/
https://ec.toranoana.jp/tora_r/ec/cot/circle/LUPAE36P8U7NdE6pd687/all/
https://www.animenewsnetwork.com/encyclopedia/people.php?id=695
http://doujinshi.mugimugi.org/browse/circle/2466/Kaishaku/
http://twitpic.com/photos/Kai_Seven_
