Smiley Sakai (スマイリー 酒井, Sumairī Sakai) is a student of the Todo School and 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.

He uses two techniques to race, first, using high speeds to enter a corner to get the other person to do the same, then correcting his speed during the turn. The other trick is to feint-brake his opponent, forcing them to back off while he speeds away. His face tenses up when he is racing to make him look like he is smiling, hence his nickname, Smiley Sakai.

Judging by the way that Daiki refers to him with the honorific san (Sakai-san), it can be inferred that Smiley is a senior student of the Todo School, and probably the reason why he knows much of Todo's experiences in racing, especially the school's rivalry with Purple Shadow and their top racers.

Car Honda Integra Type R (DC2)
Year 1998
Plate 32-094, classification 55, 5-806 classification 58 (Initial D Arcade Stage Zero)
Body Color Championship White
Custom Parts Spoon Carbon Bonnet, SSR Type V wheels (black), aftermarket turbocharger, Todo School Original Muffler, Advan Non-Reflective Fender Sticker