Ishibumi is born and raised in the Chiba Prefecture of Japan.
He is a big fan of Pokémon and has collected every form of Gundam merchandise, which he writes about in his blog.
In 2005, Ishibumi received a special prize in the 17th Fantasia Awards hosted by Fujimi Shobo for the light novel Denpachi that he submitted. He made his debut with that novel when it was published in 2006 as a tankōbon. The same year, he published his second light novel Slash/Dog. Two years later, in 2008, he began publishing the light-novel series, High School DxD. The series was adapted into a manga and an anime series. While preparing the light novels, his father died.