Riku Kaitani  

Rik-kun, Riku-Riku, 甲斐谷陸

A student in the first year of high school (Grade 10) is a grey-haired boy who taught Sena how to run. He saved Riku from bullying when he was younger and later taught him that being fast would protect him from bullies. However, Sena used his speed for bad purposes by becoming a gopher, which helped build up his abilities. Despite this, the student left Sena's school because his family needed to move. Later on, they met again in the series, and it was revealed that he could quickly identify Senas true identity as Eyeshield 21.