I went through and compiled a full walkthrough for everyone who is struggling. I did not do the thing a lot of VN walkthroughs do and use the save system to keep track of branching paths, instead each path is given a full walkthrough separately. This is useful for people who only need one or two more paths to finish, but it can also be used to start from a blank file and get all the endings in rapid succession (CTRL key is your friend in this situation).
These paths are not the only way to reach a given ending, but I tried to find simple ways with the least number of choices to reach each ending. This game is amazingly put together, and trying to figure out every branch and every little change to each ending would be a gigantic amount of work. I just want to say that
Saberoge did a fantastic job on this game.
Not much in the way of notes is necessary. About the only thing that might confuse people is that I just call the renameable native girl Native. Also, keep in mind that there are scenes you will miss following this guide. For instance, when you meet Weiss, you can answer "Let her go" in order to see a scene with three girls in the spring. This guide never takes that path as it meets up with the same path as going with Weiss only with more choices to confuse people.
And now, here's a completed save. Unzip it into your game directory so that the persistent file ends up at
<GameDirectory>\game\saves\
You may also need to put the persistent file at
C:\Users\<Username>\AppData\Roaming\RenPy\boat-1517739411\
Since I don't know which place Ren'Py loads from if the files don't match.
Keep in mind that the only thing this unlocks is ending replays as there is no gallery.
Also, I attached a text version of the above walkthrough so it's easier to read in a text editor.