I've noticed people like to dump on this author a lot, but I think this is the first thing I've read of hers (I think it's a her, anyway), and I liked it. There's a grittiness to it that I find enjoyable.
I like to see the ending as being taken one of two ways. One being that Kiwa is going to get her revenge porn, making Ririko fall for her, only to break Ririko's heart, who will then feel like garbage, same as Kiwa did right after graduation. Two being that after they have a crazy sex romp, they realize they both had feelings for each other throughout highschool and have rekindled them.
Both those routes sound like a fun read to me.