Hyouka(2001)

Oreki Houtarou is a self-proclaimed "energy-saver" - that is, he will not actively waste energy doing things that aren't necessary. Though he had no interest whatsoever in joining any clubs upon entering Kamiyama High School, he was commanded by his older sister Tomoe to enter the school's Classics Club, which was in danger of getting abolished as all previous members have graduated. Together with his old friends Fukube Satoshi and Ibara Mayaka, as well as the elegantly ladylike and curiously inquisitive Chitanda Eru, the newly reformed Classics Club find themselves involved in all sorts of mystery-solving escapades. Houtarou soon finds out that the Classics Club, as Tomoe has promised, is actually "quite interesting".

Note: Book one of the Koten-bu Series.