Before the story, he was the man Kaoru was making love to in the Special Ability classroom during her debut. He was embarassed and ran out the room after being caught by Yuki and Yuka. Years later, Kaoru would take responsibility and marry him sometime after graduation. Mr. Hyuga was seen during the flashbacks, telling Kaoru to be careful, since she is pregnant and has even fainted once. He and his wife help deliver Mikan when Yuka visits them. He also was seen in flashbacks helping Kaoru and Yuka in missions.
He became injured from the fire when he saved his daughter, Aoi, and even though he was injured, tried to stop Natsume from going to the academy. At the end of the Hana Hime Arc, he came to pick up Aoi along with Ruka's Mother and shared a hug with Natsume through the gate.
He has the Fire Alice like Natsume and Aoi, who later lost her alice. Natsume described that his alice was useless, indicating that his alice is not as strong as Natsume's Fire Alice.
- Even though Natsume talked about his father with disdain, he cried when Mr. Hyuga came running from the hospital to stop him despite his injuries and also hugged his father when he came to pick up Aoi, showing that Natsume nevertheless cares for him.
- Many fans seemed to be mistaken in thinking his given name is 'Ioran'. In truth however we don't know his name. 'Ioran' was a mistranslation on a previous translator's part; the kanji for the raw page of that chapter actually reads 'Igarashi' which is Hyuga Kaoru's previous surname before marrying Natsume and Aoi's father. Yukihira Izumi wasn't calling out to Natsume and Aoi's father at all. He was reprimanding Kaoru (which if you go back makes sense as a few pages later he addresses Kaoru as 'Ioran' in the mistranslation, which isn't logical if one is assuming that Mr. Hyuga is Ioran as Mr. Hyuga as well fled the room by that point. It should be Igarashi in both cases.)