In 2004, he enrolled in Kansai University Law School's Legal Professional Training Course, completing his studies in 2007 and obtaining a Juris Doctor degree.

In 2013, Kamiya founded a YouTube channel named "ChGrandStrategy", promoting far-right politics, historical revisionism, and conspiracy theories.

A year later in March 2020, he formed the political party "Sanseitō" alongside Manabu Matsuda, Yuya Watase, and Tsuneichiro Shinohara, and assumed the position of Secretary General.

On January 30, 2023, five senior members of Sanseitō, including Kamiya, were sued by the NHK Party on the grounds of fraud.

In response, the NHK Party filed another lawsuit on February 2, 2023, claiming 100 million yen in damages against the Sanseitō and Kamiya.

[12] In one of his own publications, Kamiya stated, "The powerful, who aim to create huge profits by selling vaccines and medicines, are actively calling for the wearing of masks through mass media such as newspapers and television in order to excessively inflame fear of the COVID-19 pandemic."

When Kamiya appeared on a televised interview on August 18, 2022 after being elected to the House of Councillors, he said, "It is true that Jewish capital is involved, but I think it was wrong to write it in such a way that it could be misinterpreted as if it were all done by Jews, so I will have to correct it in the future.