Personality Sadist BUT Sexually Masochist

From MangaHelpers:

Airi has some sexual experience, but she has never orgasmed. When her boyfriend points this out rather bluntly, she dumps him. In her search for her own orgasm, she accidentally spills her troubles to a glasses-wearing classmate named Iori. Iori may not have sexual experience, but he has been studying intensely to be a good lover in the future. While their quirky relationship starts out with him trying to help her reach orgasm, it soon becomes clear that there is much more between them. [tethysdust]