It transpired that his family did not show up that day to collect him from school, so Bi offered to carry Wang home.

Bi Mingzhe help his classmate Wang Li button his shirt.

"I just felt he was so lonely and helpless," Bi recalled.

After Bi exerted himself for almost half an hour getting his classmate home, Wang did not thank him for his effort.

"I used to be extremely shy and frightened of speaking to strangers," Wang explained. Since then, his personality developed so much that he came to accept his difference.

As he grew up, Wang's parents not only sought to console their child about his disability by teaching him the stories of Zhang Haidi - China's very own Helen Keller. They also spent a fortune fruitlessly attempting to find a cure.

Since his parents were often busy with their work, the responsibility for collecting Wang from school used to fall on his grandparents. As Wang grew older and heavier, the task became too great for his aged grandparents.

When Bi heard about the situation, he offered to take Wang to school and home again from then on.

Six years later, the assistance Bi spontaneously offered turned into a daily routine and then a promise.

"To be honest, I didn't give much thought to what would happen in the future. I just wanted to help," Bi said.

Bi's mother was supportive of her son. "You are not good at physical education classes. Now you have the opportunity to take some real exercise," she used to joke.

More than mere exercise, the experience proved to be a physically demanding task.

To pick Wang up, Bi had to get up at least half an hour earlier in the morning, before he carried him 1.5 km to their school, making four trips each day.