Well, I lied, I said I wasn't going to read more but I ended up reading the eight chapters that are translated (in Spanish). A summary of those chapters:
Chapter 5 was even worse than chapter 4 in my opinion. Asphyxia, Airi threatened to throw Hina out the window and "watersports". Also they have been caught by Hina's friend.
Chapter 6 was "cute" the first half (breastfeeding, a bit too NSFW considering they are in middle school) but Airi didn't liked to see Hina happy so she started to physically abuse her
Chapter 7 Eating insects isn't that disgusting to me compared to drinking urine, but it seems like Hina was really disgusted by it, puking again
And chapter 8 the worse. In this chapter we see that Hina talks with Airi about the person who caught them, but we see Airi only cares for her fake reputation (some of her friends are fake friends) and not for Hina and her pseudo-masochism so she decides to leave her, I even started to doubt she's even lesbian in the first place
I believe Hina isn't a masochist, but she really loves Airi and that's the reason she accepts to do wathever she wants.