Himegoto Asobi - Probably my favourite yaoi of all time, with a mature couple and fully consensual sex. The seme is a gay man who respects the uke's boundaries, while the uke is an originally straight man who starts out interested in experimenting with gay sex and later develops romantic feelings for the seme. Despite this (potentially disastrous) setup, it doesn't fall into any of the common cliches of blushy virgin uke or macho forceful seme. Neither of them shy away from having sex, and heck the uke was actually the one to proposition the seme at first. On top of that the chemistry between the couple is honestly great, I highly recommend it.