Hi. I recently picked up the game, and it is very interesting! However, I have no idea what it means when an option is greyed out. Can I not achieve it this run due to past choices? Can I not do it until I do the other route? Do I unlock certain routes as I achieve more CGs/Endings?

For reference, I am doing the Nozumi route, and during the first Hypnosis scene, I decided to rename her Yukiko.