Completing routes without a guide - which games are hardest?

Tsukihime wasn’t that hard, but Kagetsu Tohya was tough. Still haven’t finished it. I also had to resort to a walkthru for the Takashi/Tsugumi path in Ever 17.

I really needed the guide for Kaho’s path in Crescendo.

Sometimes the coises doesn’t make any sense at all and it becomes so boring that you just don’t want to try finding everything by yourself (-> Amorous professor Cherry <-).