These are 2 yaoi manga's that are a bit more well known, and I really like. (You can find any series I post on mangago)
Tight Rope by Natsume Isaku
Plot - The son of a sick mafia boss is constantly pressured to inherit his position as the "5th".However, Ryuu wishes for nothing other than to marry Naoki and have a happy family. How will this go? Let's go back to the basics, in short, the more populair yaoi series. Tight rope is really one of my favourites, since I also like Yakuza! I do wish this would be longer, since it's so good! I you haven't read this yet, you really should, and if you've only seen the anime I would still recommend to read the manga aswell! ofcourse I like the Uke's and Seme's personalities aswell, and it adds great comedy to the story~
Crimson Spell by Yamane Ayano
Plot - In order to protect his people from attacking demons, Prince Val uses a demonic sword and curses himself in the process. He leaves his kingdom to find a cure, and his search leads him to Hallwil, the person rumored to be the only one who knows how to break the curse. Hallwil agrees to help Val... for a price. And another back to the basics, a populair yaoi series. Most people will ofcourse the of Viewfinder while thinking about Yamane Ayano, but I personally like Crimson Spell a little more, since I love the supernatural story. It's just like the perfect mix between smut, supernatural and drama. Since some chapters sometimes have a little less plot in them, and some have so much story to them that you just get really into the story written behind all the smut. It's just a great overal read, with lots of chapters and still ongoing. It doesn't update a lot however, and when it does the chapters are extremely short, but it's still worth checking out if you haven't already!