The Ketsuryūgan (血龍眼, literally meaning: Blood Dragon Eye), is a dojutsu of the Chinoike Clan that appears selectively among its members. The Ketsuryugan is recognised by uts reddish color, giving a the user of this dojutsu an ominous reputation that is rather known across the Land of Water, characterised as holders of "eyes as red as blood". Since the collapse of technology and humanity, the Chinoike Clan's dojutsu rose to power toppling and replacing Rinnegan as one of the "Three Great Dōjutsu" following the dynasty that has prospered by their clan leaders Sōma and Isamu Chinoike; "The Eel King" (ウナギの王, Unagi no ō) and "Black Witch Queen" (黒い魔女の女王, Kuroi majo no joō).
The Ketsuryūgan confers genjutsu casting abilities, either by making physical skin contact with the target or meeting each other's gaze. Upon which, they can hypnotise the victim in a variety of ways, or even delve deep into their minds to extract information. The Ketsuryūgan also gave the users the ability to manipulate iron, or more accurately, any liquid with a high iron concentration. As such, fitting with its moniker, the Ketsuryūgan can manipulate the blood within a living target, whether if be themselves or another being.
- When written as 血流, ketsuryū means "blood flow".
- The Ketsuryūgan's description in both appearance and genjutsu might is similar to the Kekkei Genkai of Ranmaru from the Kurosuki Family Removal Mission filler arc. It is unknown whether the two dōjutsu are one and the same. However, the anime's depiction of both dōjutsu gave a clear difference in design between them.