Shounen No Kyoukai
Ch 9? :(prev: a few years later, taiga(ruka's friend found a sex friend omega male rin working at the bar where he drinks, ruka(omega) and rin bump each other and ruka helped him pick up the omega supressant he dropped, rin inv ruka to the bar where he works, at the bar kaoru(alpha, ruka's partner/lover/childhood friend) went to pick up ruka and when he came, he suddenly had his rut(similar to omega's heat) and out of nowhere rin had his heat that is supposedly not his heat time yet and he had took his supressant, rin chased after kaoru because he is his fated alpha taiga stopped him(apparently taiga's fated partner is ruka [from previous chapter taiga found out it was ruka because his heat smells different than the rest of omega]).)
Nyaa to Nakukara Aishiteyo