The head of an animation firm in Kyoto City has denied in court that his studio stole the idea for a novel, as a man accused of a deadly arson attack claims.

Kyoto Animation President Hatta Hideaki testified as a witness in the trial of Aoba Shinji at the Kyoto District Court on Monday. Hatta said it is heart-wrenching that the incident happened due to Aoba's mistaken belief.

The 45-year-old defendant faces multiple charges, including murder and arson. He is accused of pouring gasoline in the Kyoto Animation studio and setting it on fire in July 2019. The blaze left 36 employees dead and 32 others injured.

Hatta told the trial that he rushed to the studio after being told about the fire. But he was unable to get close to the building because there were many fire engines and ambulances. He said he saw bodies being carried out from the front entrance and prayed that other people would come out alive.

Aoba claims he attacked the studio as an act of revenge because it stole his idea for a novel that he had sent to the firm.

On the plagiarism claim, Hatta said his studio would never steal someone else's work. He said all the employees came up with their own ideas and earnestly exchanged opinions about them, adding that's why the company's films became widely known.

Hatta said he believes in Japan's judicial system and expects the court will give a fair verdict.

Aoba's lawyers maintain that he is innocent. They claim he has a mental disorder and is incapable of assuming responsibility.