A 37-year-old man accused of attempted murder admitted Tuesday to stabbing three passengers in a random knife attack on a Tokyo commuter train in 2021, but his defense team argued his intent to kill was not firm in his first court hearing.

Yusuke Tsushima is indicted for seriously injuring a then 20-year-old female university student by stabbing her several times in the chest and back, as well as injuring a woman in her 50s and a man in his 30s on an Odakyu Electric Railway train on Aug. 6, 2021.

In an opening statement at the Tokyo District Court, prosecutors said Tsushima had long harbored a desire to commit random mass murder and fantasized about killing women he perceived as "successful" in life, such as those looking happy with their partners.

Rescue workers take out stretchers after passengers were stabbed on an Odakyu Electric Railway commuter train in Tokyo's Setagaya Ward on Aug. 6, 2021. (Kyodo)

But his defense team argued that his homicidal intent was insufficiently strong and that the influence of his bipolar disorder, which causes mood swings, on his thoughts and motives should be taken into consideration.

The defendant is also accused of shoplifting groceries and other items at several stores in Tokyo and neighboring Kawasaki before the stabbing incident, according to the indictment.

After Tsushima was arrested, he told investigators that the victims were "unlucky." He was indicted in January 2022 after prosecutors determined he was mentally competent to be held responsible following a psychiatric examination.

Paramedics carry a stretcher bearing a person believed to have been injured in the stabbing incident on an Odakyu Electric Railway train in Tokyo's Setagaya Ward on Aug. 6, 2021. (Kyodo)

The stabbing rampage took place a few months before a 26-year-old man dressed in a Joker's costume stabbed a man and started a fire onboard a Tokyo train in October 2021.

In his first trial Monday at the Tokyo District Court, prosecutors said the defendant, Kyota Hattori, conceived the attack on the Keio Line train after seeing media reports about the knife attack on the Odakyu commuter train.

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