Definitely Shizune's path. Despite not having the best ending, she was always my favourite girl. The other paths were great, don't get me wrong, but there just hasn't been a connection like that for the other four girls for me.
Rin was too "deep". There were too many emotions being flung around that it was almost impossible to grab one and stick to it, which I don't like. Still, great path.
Lilly was far too formal, I was constantly waiting for her to loosen up around Hisao and stop being so elegant.
Hanako made me want to punch Hisao for being an idiot.
Emi was too stubborn for me, but I did get attached to her, otherwise the plot would fall apart.
Shizune though, her route felt natural for me. Being someone who is detached from their family in a similar way, I could relate to her much better than any character. I've always had an interest in communicating with people through a different language, and the fact that Hisao learned sign for Shizune like that... It just made me smile. Her path is also the most realistic of all of them, in terms of a relationship, in my opinion. Your very first relationship will never be as complex as the ones depicted in the other four routes, so something calm was a nice change of pace. I like the friends dynamic they shared because it felt normal