Hishigi is the second member of the Taishirou. He is the main scientist in the Mibu lands, and was researching a cure for the Death Disease by the time of his death. He is also the creator of Shunron, Sasuke, Ameron, Ruru and all the other lab-created Mibu's.
Hishigi is first seen talking to Fubuki after Fubuki tells Shinrei that Taihaku is dead. Hishigi appeares after Shinrei has walked away and comments to Fubuki that he forgot to tell Shinrei that it was him that killed Taihaku and not Kyo. Fubuki tells Hishigi that if he does not like his methods that he can leave the Mibu Clan like Muramasa. Hishigi replies Fubuki and says to him that he made his choice to stay with the clan even if it means that he is walking down the path to Hell before walking away.
During his battle against Kyo, his Medusa Eyes are destroyed and he begins dying from the Death Disease, which he contracted while researching it. Akari attempts to save him, saying that if he dies, she would lose another person. Yuan also attempts to help him. Hishigi is suprised by this and pushes Yuan away, and places a force field around Yuan, Akari, Julian, Shinrei and Hotaru to protect them from his last ditch attempt to kill Kyo.
He eventually dies giving his heart to Fubuki so that he wouldn't die in his battle against Kyo, despite Fubuki's demands that he not do it. Hishigi dies telling Fubuki not to remember their time together, as it would bring him pain, as well as regrets to Muramasa that he couldn't uphold their promise. However, before Hishigi's death, he transferred his memories to Akari so that he might continue researching the Death Disease. There, she discovers that Hishigi loved children, he felt useless when he couldn't find a cure, and that he called Akari "#13" so that he wouldn't feel certain feelings (perhaps love and/or compassion), but he thought that if they had met under different conditions, they would have become friends.
Upon his death, both Akari and Fubuki regard it with sadness and anger, as Hishigi was Akari's mentor and was Fubuki's best friend. Tokito noted his death with surprise, wondering how Hishigi could have lost and died. Later, the spirits of Hishigi, Fubuki and Muramasa appeared and revived Shinrei, Tokito, Hotaru and Yuan, who had been "turned off" by the Former Crimson King.
Shunron only discovers that Hishigi was her creator/father after his death. Aka no Ou tells her before Kyo's battle with Kyoshiro, also adding: "Do you know who killed your real father? Your dear Kyo here is guilty.", after that Shunron covers her face in shock saying: "Did dad try to kill Kyo? Why would he do that?!, taking everyone by surprise.
After the very end, Shunron, Sasuke, Ruru, Ameron and the other lab-created children appears to put Hishigi to sleep, somewhere safe, and then says goodbye to him. (Even though a few of them didn't even know him)