The court found no evidence backing up Aobas claims that KyoAni had plagiarized his work.
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He then ignited the fire with a lighter and flames quickly engulfed the building.
Aoba was also heavily burned and had to undergo intensive treatment before Kyoto police could officially arrest him.
Kyoto Animation studio after fireCarl Court/Getty Images
Aobas defense said that he should be acquitted or receive a reduced sentence due to diminished mental capability.
Some 100 people are currently waiting for their death sentences to be carried out in Japan.
