In ancient times, the Oni terrorized Japan until good chi wizards trapped them within masks. The masks were then scattered across the Earth
Ikazuki's mask is found by a fisherman, but it is snatched by the Dark Hand and then by the Chans. To find out how to defeat Tarakudo, Jade uses the Rat Talisman to make the mask come to life so they could interrogate him. The reanimated Ikazuki immediately attempts to summon his Shadowkhan, but he finds he needs a host to do so. He shows interest in Tohru, but by nature, Tohru is repulsed by the thought of binding to an Oni. Some petty remarks between him and Uncle spark an argument, and in the confusion, Ikazuki escapes Section 13. What with one thing and another, Ikazuki lands face-down on a chair and Finn sits on him, resulting in Ikazuki (still thinking and speaking for himself) being bound to Finn's rear. Ikazuki summons his Shadowkhan to capture Tohru, intending to use the removal potion to have his mask moved onto Tohru's face. (He doesn't have the potion yet, so he interrogates Tohru for it, playing the "bad cop" with Finn as the "good cop.") To his fury, Finn himself uses the potion to remove the mask and abandon it -- partly in rebellion against Ikazuki's arrogance, but mainly because he has to go to the bathroom. Jade then removes the Talisman from the mask.
When all nine masks are reunited, they break, releasing the Demon Generals. They take over Section 13 and begin to spread a shadow shroud around the Earth to destroy all good magic. Ikazuki monitors their progress from within the compound, removing the onion odour to allow Tarakudo in. But Tarakudo gets the willies, sensing interference. He captures the J-Team and imprisons them in Section 13 cells. Then, the discovery of Tarakudo's mask causes a fight. Ikazuki tries to join, only to be tackled by Viper and El Toro. Ikazuki is then sucked in Tarakudo's mask, along with the other demons and the shadows.Ikazuki was later freed by Padro Lodo alongside the rest of the Oni Generals to serve as generals in the Organization's Army. Ikazuki now has an intense rivalry with Roxas due to both of them commanding samurai and being foil counterparts to one another in personality and demeaneor. He's also managed to make Vanitas his own samurai apprentice, a ward you might say.