A shaken company president has mourned the loss of his staff members.
Kyoto Animation Hideaki Hatta said he is heartbroken over the deaths of his young staff members in one of the worst mass casualty incidents in Japan since World War Two.
"Some of them joined us just in April. And on the eighth of July, I gave them a small, but their first, bonus," he said.
"People who had a promising future lost their lives. I don't know what to say. Rather than feeling anger, I just don't have words," he said.
Police are investigating the suspected arson attack at the animation production firm that killed 34 people and injured dozens more.
Tributes to the victims lit up social media, with world leaders and Apple Inc's chief executive offering condolences. The hashtag #PrayforKyoAni, as the studio is known among fans, has become popular.
One suspect is in custody but the motive for the apparent attack remains unclear.
How did the fire break out?
Local fire stations began receiving emergency calls around 10:30 am (0230 GMT) Thursday, with people describing the sound of explosions at a building belonging to the Kyoto Animation production firm.
Police said a man was believed to have doused the building with a flammable substance that he set alight.
The blaze quickly engulfed the three-storey building, trapping dozens of people inside.
Eyewitnesses said the blaze was so fierce that they were unable to even approach the building as desperate people jumped from the windows to escape.
It took firefighters hours to bring the blaze under control.
The flames gutted the building, which fire department officials said was up to date with fire safety rules.
Who are the victims?
Many of the 34 victims of the attack, in the ancient capital of Kyoto, were young women, company president Hideaki Hatta said.
Kyoto police said victims included 12 men and 20 women.
Among the company's employees was 21-year-old Megumi Ono, whose status remains unclear.
Her grandfather Kazuo Okada told public broadcaster NHK he was still searching for her.
"It turns out that (she) was on the second floor... her name was not on the list of people sent to hospitals," he said.
"I want to see her face," he said as he broke down with emotion.
Who is the suspect?
Police have detained a man described by local media as a 41-year-old resident of Saitama, an area north of Tokyo.
He is reported to have said "drop dead" before setting alight flammable liquid he poured around the building.
His motive for the apparent attack remains unclear, though he reportedly confessed to the arson after his detention.
He suffered serious burns in the fire and was taken to hospital after being detained. He was reportedly unconscious on Friday.
The man appears to have no links to Kyoto Animation, but there were reports he had accused the firm of plagiarism.
The Kyoto Shimbun newspaper reported he told police "I set the fire because they stole novels."
Public broadcaster NHK said the man suffers from a mental illness and served 3.5 years in a prison after stealing cash from a convenience store.
What is Kyoto Animation?
Kyoto Animation is a firm well-known among anime fans for its role in producing popular TV anime series including "The Melancholy of Haruhi Suzumiya" and "K-ON!"
Founded in 1981, it had 154 employees and some of its dozens of animations became popular enough to have feature film versions released.
While many animation studios are based in Tokyo, the firm -- known by fans as KyoAni -- reportedly felt strongly about remaining in the ancient Japanese city of Kyoto.
Its work often featured elaborate screen shots described as "KyoAni quality" by enthusiastic fans.
Anime fans at home and abroad tweeted their support with the hashtag #KyoAniStrong and #PrayForKyoAni.
"These are people who carry the Japanese animation industry on their shoulders," Kyoto Animation's president Hideaki Hatta told reporters.
"It's heartbreaking. Japanese jewels were lost," he said.
Have there been similar attacks?
Violent crime and particularly mass casualty incidents are vanishingly rare in Japan, which has strict gun control laws.
But there have been past instances of arson, including a 2008 attack on a video shop in Osaka that killed 16 people.
Arson is considered a particularly serious offence in Japan, where many buildings are made of wood and extremely fire-prone. The Osaka attacker is on death row.
In 2001, a devastating fire in Tokyo's Kabukicho entertainment district killed 44 people. Police investigated the blaze as an arson attack but never charged anyone for deliberately starting the fire.
More recently, there have been mass stabbing attacks, including a 2016 rampage by a knife-wielding man at a care centre for the disabled in suburban Tokyo that killed 19 people.
Additional reporting: Reuters