Weeks before the attack, college student and pop idol Mayu Tomita, 20, told police she was being stalked by a man named Iwazaki, the Japan Times reported. Iwazaki sent multiple messages to Tomita on Twitter and claimed to have sent her a watch earlier this year. The watch was sent back to Iwazaki in April.
"I will never forget that I was looked down upon by you," a message sent by Iwazaki on Feb. 22 said, according to Japan Times.
"It would be radical to kill just because (someone was) rejected by a girl," said another message, sent on March 15.
Police believe that the accused stalker might be 27-year-old Tomohiro Iwazaki, who was arrested Saturday afternoon and accused of stabbing Tomita in the neck and chest more than 20 times.
The attack happened outside a railway station in western Tokyo ahead of a scheduled performance by Tomita, according to the South China Morning Post. Officers found a bloody knife at the scene, according to the Japan Times, and Iwazaki admitted to stabbing Tomita.
He told authorities he attacked the pop idol because she refused a gift from him, the Times reported.
"I ambushed her at the station and asked her (about the gift)," police quoted Iwazaki as saying. "I lost my temper and stabbed her many times because she didn't clearly answer."
Authorities said they planned to charge Iwazaki with attempted murder.
Tomita has performed in multiple shows featuring other young, mega-popular pop idols, according to the South China Morning Post, and has appeared in children's television shows.
Violent crime is relatively rare in Japan, but it's not the first time that a fan has attacked a pop idol. Two members of the popular girl group AKB48 suffered broken hands and cuts in 2014 after a man attacked them during a fan event.