When you want to make changes in your life based on the influence of some of the characters. For example, Sakuya and Alice inspired me to become more active and productive, and Patchouli played a role in fueling my passion for science and learning.
Also, does anyone here have advice as to how I can get my brother into Touhou? At the moment, he is rather narrow-minded when it comes to the story/characters and I want to show him otherwise.