Intrigue in the Bakumatsu – Irohanihoheto (Japanese: 幕末機関説 いろはにほへと, Hepburn: Bakumatsu Kikansetsu Irohanihoheto) is a Japanese original net animation (ONA) series, created by Ryōsuke Takahashi and Sunrise, with character designs by Yusuke Kozaki.

The series follows Yojiro Akizuki, the bearer of the legendary Moon Tear Sword, who is on a mission to seal a supernatural object known as the Head of the Conqueror, which has now appeared during the Boshin War.

The series is set in the Bakumatsu era, with the Shogunate being in its final years, and war fast approaching.

The series was broadcast between October 6, 2006, and April 6, 2007, on the Japanese Internet streaming channel, GyaO.

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