Responses
maybe this one?
http://www.mangago.me/read-manga/koi_to_unmei_no_sankaku/
Okay, MAYBE this one? http://www.mangago.me/read-manga/sukijanaitte_hyakkai_tonaeta/
i once read a manga (a oneshot) about a beta x omega couple it was good and then an alpha (his *fated pair*) appeared and they had a threesome ..i hope this wont happen here too ;-;