Kono Kanojo wa Fiction desu.

Lead character is a naive boy who's fallen in love with an older girl who everyone considers a genius writer. He's so in love in fact, that he has forgotten about his secret hobby for the last 2 months. His secret hobby is that for the past 10 years he has been writing the "character profile" of a single girl. Her birthdate, personality, hobbies, conversations, etc.... is all recorded in a large pile of notebooks. All this time this fictional girl has been his friend and lover, but now that he is in love with a real girl he decided to throw them all away. In order to "purify" the notebooks, he decided to burn them at a nearby shrine. To his surprise, the sempai he's in love with was also there. It starts to rain and as t...