The suspect was angry that Japanese singer Mayu Tomita returned a gift he gave to her, police said.
A popular Japanese singer is in a coma after being stabbed by an angry fan at least 20 times, police said.
The critically injured Mayu Tomita, 20, was attacked near a concert site Monday by a man who had been stalking her, authorities said.
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Police arrested Tomohiro Iwazaki, 20, who told investigators he was upset with the young singer, who is also a college student, because she returned a present he had given her.
"I ambushed her at the station and asked her [about the gift]," Iwazaki told police, according to the Kyodo news agency. "I lost my temper and stabbed her many times because she didn't clearly answer," the man was quoted as saying.
Witnesses called police after witnessing the attack, authorities said. Tomita was critically injured, with stab wounds across her neck and chest, police said.
A bloody folding knife was found at the scene, according to officers. Tomita was scheduled to give a concert near the site where the attack took place.
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Kyodo reported a man with the same name had been making threatening posts to the singer's Twitter account.
In May 2014, two members of the Japanese group AKB48 were attacked by a man wielding a saw. The suspect pleaded guilty and was sentenced to six years in prison.
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