A 24-year-old man who attacked two members of the idol group AKB48 with a saw at a May event in Iwate Prefecture pleaded guilty at the first session of his trial, but used unusually colloquial language when responding to a question from the presiding judge.

Satoru Umeda, an unemployed man from Towada, in neighboring Aomori Prefecture, stands accused of assaulting the two AKB members — Rina Kawae and Anna Iriyama — with a saw, at a fan event in Takizawa, Iwate Prefecture, on May 25.

After prosecutors read out the assault charges in court, presiding Judge Takehiko Okada asked Umeda whether he accepted the charges.

"Yup," Umeda replied.

Prosecutors told the court that Umeda committed the violent act because he was dissatisfied with the "boring life he led every day, with no income or jobs, after being fired from a job as a security guard."

"I felt that I was completely opposite the AKB members, who earned a lot of money, and wanted to vent my frustration at them," prosecutors quoted Umeda as saying.

Defense lawyers said they will not contest the charges against Umeda.