I don't think there's any manga that'll evoke the same feelings reading Saezuru :( You can try these mangas though. Some of them are short, others are webtoons.
Yatamomo
Harada comic, completed. Momo mooched off on others and sold his body all his life ever since his mother gave him to a customer to use. Was picked up by a guy named Yata who's the type who can't leave stray cats alone. Heavy themes but with a happy ending.
http://www.mangago.me/read-manga/yatamomo/
MODs and its sequel Nights Before Night
First one revolves around a gay prostitute nicknamed as 'Shiro' and a newly-hired driver. Pretty straight forward, also lived his life as a prostitute (but before that, his father sexually abused him). Shiro and sequel's pairing share a past with a deceased man named Shigure. They're all trying to move on/recover from this man's death. Enjoyed both equally.
http://www.mangago.me/read-manga/mods/
http://www.mangago.me/read-manga/nights_before_night/
Scarlet Beriko series, three of them but the one that's closest to yakuza like stuff is the latest sequel of the three, 'Jealousy'. No need to read the first one (Minori no Te) but the second one inroduces the main character of the third:
http://www.mangago.me/read-manga/minori_no_te/
http://www.mangago.me/read-manga/yondaime_ooyamato_tatsuyuki/
http://www.mangago.me/read-manga/jealousy_scarlet_beriko/
Dark Heaven
Tackles themes such as racism and homophobia. No seme/uke. The couple switches. It can get dark but the pairing is incredibly wholesome. Compelling drama, and the characters are all so interesting to read, The art is more akin to western comics even if it's a korean manhwa. Highly recommend this one. It's complete too!
http://www.mangago.me/read-manga/dark_heaven/
The 'Abusive Lover' Series by Ogeretssu Tanaka
(1 Azami, 2 Sabita Yoru Demo Koi Wa Sasayaku, 3 Ch.4-6 of Renai Rubi no Tadashii Furikata and 4, Hadakeru Kaibutsu + Extra - page 15 of Narrow Place Collection)
A hell of a ride, intertwining stories, all connected to the past. It's Tanaka-sensei so expect raw emotions from the character's expressions. It's not finished yet but it's really good!
http://www.mangago.me/read-manga/azami/
http://www.mangago.me/read-manga/sabita_yoru_demo_koi_wa_sasayaku/
http://www.mangago.me/read-manga/renai_rubi_no_tadashii_furikata/
http://www.mangago.me/read-manga/hadakeru_kaibutsu/
http://www.mangago.me/read-manga/narrow_place_collection/
STORIES BY YONEDA KOU
Doushitemo Furetakunai and its sequel Soredemo, Yasashii Koi o Suru
A lot more light-hearted compared to Saezuru but it still evokes the feeling Yoneda-sensei writes. The characters feel real as well as their struggles. I prefer the sequel.
http://www.mangago.me/read-manga/doushitemo_furetakunai/
http://www.mangago.me/read-manga/soredemo_yasashii_koi_o_suru/
Reply
It's a short story released inside 'Nights'. It's about a straight man falling for another straight man. Just like all sensei's other works, the feelings and characters feel real.
http://www.mangago.me/read-manga/reply/
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just a couple of short shounen-ai that provokes melancholic feelings
http://www.mangago.me/read-manga/3_ban_sen_no_campanella/
http://www.mangago.me/read-manga/kimi_wa_natsu_no_naka/
Well, yes?
I love saezuru, it's even in my top ten, but not the first. Depend on your tastes.
Saezuru is my absolute favorite. Complex characters and a plot no wholly centered on the romance...it's a tough act to follow. Try Ten Count
Oh..Walk on Water is a good one too. Great sexual tension, character development and plot
Scarlet Beriko's Jealousy. It's a multipart, but I think that's the first one in chronological order.
Is there a yaoi manga as good as saezuru?