Yay. thank you!! I feel like at least 50% of the time I’m reviving old clubs rather than participating in current ones 
And I have also finished! And greatly enjoyed reading through everyone’s commentary now I’ve finished too! (apologies quite long rambly thoughts)
Thoughts on chapter 3:
Right off the bat Ryuuji being a rapist was incredibly jarring. So far seems like the only point of this is to tell us he’s a bit of a bad guy (rather than the actual fact he should be in jail and not the friend to our protagonist).
And second quite jarring reveal that Sadako is intersex, which felt like it came with no build up, and was a lot for shock factor.
Both of these reflect the time it was written in (and perhaps the genre/style?), but I feel like it’s still not fully forgivable, there’s plenty of literature which doesn’t play to these tropes.
But annoyances out of the way:
The whole structure of having a countdown clock to our chapter 3 worked really well in building up the tension (although I admit that I felt a bit info-dumped upon in the middle of ch3).
竜司’s (slightly overpowered) deduction skills/just general effort of connecting the dots felt fun. (e.g. blinking being the video’s black frames - which I felt a bit of a rush being roped into the discovery at the same time as 浅川).
Aside: - lol at how much I got used to reading 仮に in this section.
Similar to @Naphthalene, up until now I’ve noticed a lot of foreshadowing around reflections, so during reading ch 3 I was thinking this would somehow be an important part of the curse.
And the ending of ch3 was very tense, and actually discovering the skull felt very occult/mystic.
Thoughts on chapter 4:
I sort of expected as such (too many doubts left towards the end of ch3), but the curse isn’t cleanly lifted just by finding Sadako’s grave.
I had also picked up on foreshadowing around virus’ earlier, so as soon as 竜司’s final scene started I was on the same wavelength as him, and had seen that 浅川 escaped because he shared the video. (Although 浅川 later seemed to be convinced this also includes the requirement of making a copy of the tape - which I didn’t see as obvious)
And like @bungakushoujo I read it as us being told 竜司 was gay. In my head there was the implication he’d made up this persona to hide out of shame/embarrassment - which I think given society at the time, may have been more obviously read between the lines.
And the ending pretty satisfying for me, we’ve got 浅川 talking out his last reservations, but ultimately deciding to try to save his family & unleash the virus (which I felt nicely wraps up the book, but also leaves a lot to happen in later books)
But yes, that’s a likely explanation. He did willingly sacrifice himself for his friend, after all. His lies had so much detail, though - if they were lies. I still think he might appear in the next volumes and his backstory could be explored more. Although I’m not sure there was a plan for a whole series from the start. If not, then the things that are left vague in this book were originally supposed to stay vague forever. 
, but it did remind me I should read this book. So I’ve started too.
