According to local media reports, the 41-year-old told police he planned the deadly blaze after the company stole his novel.
A witness told reporters that he “seemed to be discontented, he seemed to get angry, shouting something about how he had been plagiarised”.
The blaze in Kyoto is the worst mass killing since a suspected arson attack in Tokyo killed 44 people in 2001.
It is believed the suspect shouted “die!” as he poured a liquid, believed to be petrol, around the studio.
The blaze broke out at 10.30am local time on Thursday and was fully extinguished at about 6.20am on Friday.
Officers said the suspect was not a company employee but gave no further details.
More than 70 people were in the three-storey building at the time – and 10 people remain in a critical condition.
Of the 33 who died, 19 were found on a staircase leading up to the roof from the third floor, with authorities telling the Kyodo news agency that their bodies were found piled on top of each other.
The victims may have rushed up the stairs to escape the blaze on the lower floors, only to find that they could not open the door.
None of the victims’ identified have been disclosed, but locals suggested many of those who died would have been in their 20s.
Two cans, a rucksack and a trolley were found near the site, and television footage appeared to show five long knives being laid out by police as possible evidence on the ground outside the building.
Little else is known about the suspect, who is under police supervision with serious burns to his face and legs.
