I forgot another title

bl manga, the seme can smell his soulmate's (the uke) scent, but it has a side effect if he smells it for too long, he gets overstimulated(I think) at first, the uke is afraid of him, but they eventually get closer. one day, they go to a park together, and the seme faints because he was exposed to the uke's scent for too long. when the uke brings him home, he meets the seme's older sister. she says something like, 'are you sure you're his soulmate? we can smell more than one person, so it's not guaranteed that you're the one.'