[Tanjiro x Senjuro] The former Water Pillars Tsuguko and Rengoku's younger brother.. They're just friends, right? When Tanjiro follows his crow to the Rengoku estate and meets Senjuro, a new fate was unraveled. The two go on plenty of adventures together (and run from Inosuke), but they just stay friends. Until one day, when everything gets messed up.