Taniguchi is comically lascivious; he gave a 'score' of attractiveness to each first-year girl based upon his tastes and preferences. He remembers the full names of everyone receiving an 'A' rank, with Nagato receiving an A-. As for Mikuru, her mere presence elicits an altered state of adoration for Taniguchi and Kunikida, especially when she was in her soba-serving costume. He also knew Haruhi from back in junior high, and was Kyon's original source of information on Haruhi before he started conversing with her. It is hinted that he may have been the person that dated Haruhi for the shortest amount of time.

From Wikipedia