So even in the fourth playthrough you still get some new notes, although they're mostly just flavor at this point and don't reveal anything substantial. The notes in the scarecrow puzzle were also different and I guess there's the notes from the "fox clan" at the end of the true ending route. None of these count for achievements since I already got all of those
Fifth playthrough all I got was the final journal regarding Kotoyuki after getting the true ending, which pretty much describes Hinako's character's final resolve and her outlook towards the future. Then I went for UFO ending so guess I am done with SHfaggots
IMO, this game demands way too much from the modern adhd player to get the full picture, and you probably have to be the kind of autist (that I happen to be) who likes to explore every nook and cranny, several times, and also replay a linear story game, several times (even if you can skip entire sections) to get it, because the endings add new story details on top of alternate outcomes. I ended up liking Hinako and especially Foxguy much more than I did at the start