Aoba is referring to the public contest held by Kyoto Animation which required participants to send in draft novels, with the winners getting promised that their stories would be turned into anime. This contest was held before the attack.

However, the allegations of plagiarism and the plea made by the defense were denied by Kyoto Animation.

They further argued that Aoba believed a female director at Kyoto Animation, who he had admired, had stolen the novels he submitted. Her success compounded by his own failures fueled a hatred in him, which also played a part in Aoba’s crime.

Man, this is why many studios stop running these kind of competition and won't accept unsolicited submissions. People would claim the company stole their ideas even if it's developed independently.