Legal Talkback: negligence in saving others, guilty or criminal?

Jiang Ge, a 24-year-old Chinese student from Qingdao, Shandong province, was killed at her apartment in Tokyo on Nov 3, 2016. The murder case has attracted wide attention online as Jiang's roommate Liu Xin did not save her when the murder was happening on the other side of door. Is it just a guilty or even criminal when there is negligence in saving others?

Source: screenshot from video