Muchi Nochi Tsugai

When Hayato, an omega, hears about the concept of fated mates from his friends, he jokingly says that he would meet his if he could. On his train ride home one day, he suddenly smells something sweet and wonders if it's the pheromones of his fated mate. Sadly, he doesn't find that person in the crowd, but little does he know that Asahi, an alpha, is there and smells the same sweet scent.

(Source: GOT, translated)