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I don't really good at explaining(in english) but I'll try my best.
In ch. 3/4(?) we've seen that actually hibiya just a test subject for his research but that's just his reason to be close with him, because hibiya is his fated partner they met along time ago when hibiya still work on that cafe... Hibiya remember and then mated with him :3 and in ch. 5.5 it's kinda like spin off (?) about their life after that
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Ok,yeah.... I kinda got that. But it doesn't explain a lot. I mean, was he employed on that lab because of that? And is Hibiya still working there after the incident? Why were they having a long distance relationship? What was the deal between Yagami's father and Hibiya? And what was Hibiya's trauma about? And was that couple Yagami's father with his omega partner? And it says that Hibiya is a year older than Yagami, but according to that memory at the caffe,it must be more the age gap
Is it just me or that fifth and extra chapter were messy, confusing and quite... incomplete? I've got the feeling that I didn't understand what happened (⊙…⊙ ) I mean, I didn't get what was going on with Yamagi's father, what was that deal with Hibiya, or why there was a long distance relationship, if they were in Japan or United States with Sana, if Hibiya was still working on the lab or not, why was Yamagi using Hibiya for his research... among a lot of other things... like, what?!
I am becoming dumb because I'm sleepy and it is 1am here or it was like there were some missing pages at those chapters ( ̄∇ ̄")