Satsujin Kippu wa Heart-iro(1990)

Satsujin Kippu wa Heart-iro

A detective story about a murder on a train based on a series of young-adult novels for women by Hiroyasu Yamaura. While suspended from school after beating up the seniors who bullied her best friend, Seiko goes for a trip to Nagasaki, where she finds herself involved in a murder mystery.

(Source: Shoujo & General Weblog)