*first glance* For the most part, it seems to just be the one couple. Let's see what the raws say! *checks vol 1 raws* ... Odd. Very few tags, no comments. *skims 20 pages at a time* ... Okay, chapter 6 features a different girl. *next page* ... On the one hand, expected another guy to show up, on the other hand, dammitdammitdammit-- *next page* ...? Odd, but, alright then. Guess I'll take a crack at this.
Vol1Assessment: Guy1 and Girl1 seem to be in a relationship, he goes with Girl2 at least once, Guy2 shows up and menaces menacingly to no apparent effect. Vol2Assessment: Guy1 cheats again at some point, things get awkward and Guy1 and Girl1 seem to break up for a bit, Guy2 goes about shifty business and gets a lot more screentime than he did in volume 1, Girl3 has a few partners, Guy1 and Girl1 have "A Talk" cliffhanger. Vol3Assessment: Guy1 and Girl1 seem to make up, Girl3 has a 'thing' with Guy2 though he still seems to be shifty-eying up Girl1 still, Guy1 gets with Girl2 again goes back to Girl1, PlotOriented/LessSexMoreDrama chapter ensues ending with Guy1 and Girl1 together, but wait, Guy2 comes right back for (dare I say it?) more shifty business, almost clears his goal, BAM Guy1 appears with impeccable timing (not counting the possible shifty business I may have missed involving Guy2 and Girl1 since the beginning) and takes Girl1 away with him, after which a bit more drama comes up and seems to end with them together.
Vol4Assessment: There is no Vol4, at least, not up on the site. And admittedly, there really does seem to be a stark lack of tagging opportunities presented.