Such a great story I'm dgbsdvklsgbk
You're thinking of shounen ai, mate. Yaoi is a genre with gay sex or gay sexual content. Romance or happy endings are irrelevant. It can be heavy or light on plot but it will have sexual content.
Shouneni ai is boys love. Its a love story genre and thus sex or sexual content is irrelevant and typically very light. It doesnt guarantee a happy ending either, both genres could have tragic endings.
KS is yaoi. It has gay sexual content with a m/m lead pairing. It has a plot but as yaoi genre, it doesnt require romance.
This isn't yaoi..there wont be really a happy ending :/ The cop will probably be the hero OR die and horrible death.