Well have you read Sekaiitsu hatsukoi? It took them 18 years... itsredhoneyrose
I know it's not a yaoi too, but I'd like to also give a shout out to Skip Beat where they're *still* not an official couple, and it's been ongoing since 2002.
But ugh hearing SIH has been 18 years makes me feel ancient, I remember when that series *started*...... Oh geez....
Its been almost 5 years since I started this and they are still not together