Asahikawa District Court in Hokkaido has sentenced a 20-year-old woman to 23 years in prison in a high-profile murder case in which a female high school student died after being pushed off a bridge and into a river in Asahikawa in April last year.

According to Friday's ruling, the woman, Yuka Konishi, conspired with Riko Uchida, 22, and others to drive the then 17-year-old victim from Rumoi to Asahikawa and assault her between April 18 and the following day. They forced her to fall into a river and die.

"The way the crime was committed was cruel and extremely malicious," Judge Yoshihiro Ogasawara said in handing down the ruling, adding that the defendant "showed no attitude of respecting the victim's life and integrity."

Konishi's 23-year sentence came against the prosecution's request for 25 years.

During her lay-judge trial, the defense said that the incident was orchestrated by Uchida after the victim posted a photo on social media without Uchida's permission, adding that Konishi played only a subordinate role.

However, the court found that Konishi was actively involved, noting that she beat the victim in anger after the victim called for help.

Following the ruling, the victim's family released a statement through a lawyer, saying that they cannot forgive the defendant but want her to seriously reflect on what she did.