Sakai

Another driver and current student of the Todo School, Smiley Sakai (スマイリー 酒井, Sumairī Sakai) is one of Daiki's friends and drives an Integra Type R DC2, equipped with an aftermarket turbocharger.
Sakai races against Keisuke of Project D in a hillclimb battle.
His face tenses up when he is racing to make him look like he is smiling, hence his nickname, Smiley Sakai.

(Source: Initial D Wiki)