Ikkaku Madarame vs. Shūhei Hisagi is a brief clash between 11th Division 3rd Seat Ikkaku Madarame and 9th Division Lieutenant Shūhei Hisagi during the Kasumiōji Conspiracy over their opposing views on how to handle Ichigo Kurosaki's actions during the ongoing Coup of the Kasumiōji.
Ōmaeda is resting outside the 2nd Division barracks, whereupon he is approached by a Shinigami who tells him that the security team is in position, and asks for further orders. The Shinigami is surprised when Ōmaeda tells him to stand down, as there are other Divisions taking action, particularly the 3rd Division. Ichigo Kurosaki questions Amagai's motives in helping them, to which he says that he has his own reasons.
As they run off, two Shinigami from the 7th Division observe Amagai's involvement with the Substitute Shinigami, and immediately leave to report this to their captain. Later, Captain-Commander Genryūsai Shigekuni Yamamoto is informed of the 7th Division's observation by a messenger, and decrees that Amagai must be apprehended at all costs.
Meanwhile, several 11th Division troops run down an alleyway, declaring that they have the right to apprehend the criminals. However, they are stopped by the lieutenant of the 9th Division, Shūhei Hisagi, who tells them to return to their barracks. Contrary to his instructions, the 11th Division members prepare to engage in combat with Hisagi, only for the 3rd Seat of the 11th Division, Ikkaku Madarame, to interrupt, stating that he'll be his opponent.
Captains Shunsui Kyōraku and Jūshirō Ukitake walk down a corridor, whereupon they are informed by Shunsui's Lieutenant Nanao Ise that fights are breaking out all across Seireitei. Meanwhile, Ikkaku clashes with Hisagi, stating that all the lieutenant is good at is defending. Ikkaku splits Hōzukimaru into three sections, causing Hisagi to momentarily falter, before clashing once again in midair. Ikkaku swings his Zanpakutō at Hisagi once more, who backs off, telling him to return to his Division's designated area. Ikkaku disregards his order, saying that Ichigo is doing this because he knows something that they don't. As they each exchange blows with their sword, they continue arguing their case. Ikkaku states that once he fights with Ichigo, he'll understand his motives, but until then, he vows not to let another Shinigami touch him, and promises to kill him if Ichigo really has changed sides.
After his brief fight, Hisagi directs his search squad into four groups. A member of the squad asks him whether they should patrol another area, but Hisagi states that that area belongs to the 8th Division. He continues, stating that they'll just continue getting in fights with other divisions if they enter their territory. As they split up, Ikkaku redirects his troops, as Lieutenant Chōjirō Sasakibe reports back to Yamamoto, stating that most of the rebellion has been quelled.