The family of a teacher murdered in Japan pleaded with her suspected killer's parents to "redeem some self-respect" and help to trace him.
The body of Lindsay Ann Hawker, 22, from Brandon, near Coventry, was found taped up and half-buried in a sand-filled bath on the balcony of Tatsuya Ichihashi's apartment in Ichikawa, east of Tokyo, in March 2007.
Ichihashi, her former student, has been on the run since.
A letter, from parents Bill and Julia and her sisters Lisa and Louise, was sent to his parents, saying the murder should be on their consciences.
It said: "We know you may feel ashamed about what your son has done, but we ask 'what can you do now to help us?'
"We are just an innocent, grieving family. Surely you could redeem some self respect if you would make a public appeal for your son to give himself up? Or, to ask that whoever may be protecting him, give him up.
"We feel sure that you would regain some respect from the Japanese people if you were to publicly state that what your son did was deplorable, and that by giving himself up, he would bring back some respect to your family, and to the Japanese people.
"As a family, we still struggle to accept that this has happened. You must surely understand how this feels.
"We understand how difficult this may be for you, and how ashamed you and your family must feel. However, we want you to understand that as long as you live, this murder will be on your consciences and we will remind everyone at every given opportunity of the terrible crime that your son committed."
Police hunting the English teacher's killer have raised their reward to 10 million yen (£63,000) in an attempt to revive the two-year-old investigation.
Since Ms Hawker's death, her family has visited Japan several times, appealing to police and the public for help in finding the suspect.
The letter to his parents continued: "Lindsay was an amazing beautiful, young woman, who, having graduated from Leeds University with an honours degree in July 2006, travelled to Japan, to teach English.
"Your son, followed her, and begged for lessons. He followed her to her home, and managed to persuade her that he was a genuine person, wanting help to try and improve his English.
"We will never give up this fight for justice for our daughter. She was too precious. Your son has had two years of freedom, something he does not deserve, having taken our daughter's life."
"The sooner he is caught, the sooner that some peace can be brought to both families. We can grieve the loss and you can regain some respect in society, knowing that your son is paying for the crime."