Yuhei, who died in January, is the latest in a string of victims of bullying, or ijime, which bedevils Japan's schools - otherwise known for their strict discipline. Last year 22,000 cases of violent bullying were reported - the real number is thought to be much higher. A six-month investigation by police in Shinjo, 200 miles north of Tokyo, could not find out who bullied Yuhei - an indication of how deep-rooted and insidious the ijime phenomenon has become.
Education is a serious matter in Japan. Schools and colleges form a closely monitored system which excels in producing hard-working citizens pre-tuned to Japan's hierarchical society.
But for some, the system crushes all their individuality until they conform. Or, in extreme cases, until they die.
'In Japan you have to belong to groups,' said Yoshiko Otsuka, an education counsellor at Kanagawa University. 'If you are a little different, you will be left out. And the education system reinforces this idea that everyone should be the same.'
The homogeneity in Japanese schools is striking. Schools prescribe for their students identical uniforms, the colour of satchels, hair length, the size of their lunch boxes, the amount of time to be spent on homework. Students listen patiently to their teachers: they are not expected to offer their own opinions. The sense of group belonging carries over into the playground, where any divergence from the norm is quickly penalised.
The government, worried by the persistence of bullying, announced in February that it would hire 14,000 child-welfare workers to counter bullying. Critics said this was only treating the symptoms, not the cause: an overly strict and inflexible education system, which breeds intolerance among pupils.
Yuhei had apparently become the sacrificial victim in his class: his family was wealthier than average and he spoke with less local slang than most of his classmates. Shortly after his death, seven boys from his school said they had beaten him and wrapped him in the gym mat. Other students said they saw the bullying going on in the gymnasium. But then the seven boys changed their stories, and all the other students clammed up.
The police were unable to break through the wall of silence, and last Monday the Family Court said it did not have sufficient evidence to take any punitive action against the accused. They were acquitted and, because they are minors, the case cannot go to appeal. 'I'm very disappointed,' said Yuhei's father, Shohei Kodama. 'It was not an accident.'