Endou-Kun No Kansatsu Nikki

Via Baka-Updates Manga: Endou's the quiet guy with the messy hair and glasses who never talks to anyone. Tsuda's the tall, indifferent guy who sits behind him in class. It's only when Tsuda's friend, an aspiring hairstylist, begins to rave about how much he wants to give Endou a haircut that Tsuda bothers to even look at the guy. But he soon realizes that he just can't stop looking, and that he may never be able to look away from that expressionless face again...