i've finished every route except Shizune's and it's really interesting to see how differently the girls develop depending on which route you pick
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like for instance in Hanako's route a lot of it is spent trying to help her get over her social anxiety problem among other things, But if you go down Lily's route Hanako manages to get over her social anxiety problem without Hisao's or Lily's help at all and much more quickly than she does when you are on the Hanako route
Personally my two favorite routes are Rin and Lily in that order. Emi's was alright and Hanako's was just full of :3 moments, her bad ending was really bad tho -_-
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Whoever wrote the story for Rin's arc was amazing there are a lot of very powerful moments during it that will either make you laugh, tear up or both at the same time. Her bad end is pretty soul crushingly depressing but the good end more than makes up for it. And unless it happens sometime during the Shizune path lily's is the only one so far that has really had Hisao dealing with his heart condition in a bad way, her bad ending was pretty sad i haven't played the good lily ending yet so i don't know how different it is