If you liked the Good-bye manga, the Anime-Planet community thinks you'd like:
Tokyo is a bustling metropolis filled with life, catering to both successful businessmen and the down and out alike. From a man who’s shackled to life because of his ailing mother to a tale of a struggling mangaka, humanity’s darker moments are revealed with sadness and shame. Whether it’s the tale of a man and his monkey or the vengeful feelings of a disfigured woman, many dreams and stories are told with insight and empathy.
Two compilations of older gekiga manga by the same author, Yoshihiro Tatsumi. While it's generally cliche to recommend something because it's the same author, Tatsumi's stories tend to be very similar: lots of dark themes, lots of sex, a pretty dismal outlook on society, and lots of unfinished ends (plenty of the stories in both compilations just 'end' without much closure, or flat out don't make sense). If you liked the style or tone of one, you will enjoy the other.
In the mid 20th century, young Hiroshi found himself enamored with manga – especially works created by Osamu Tezuka. With a strong desire to publish his own works, Hiroshi picked up a pen and began a lifelong journey to live up to his role model. Through disappointments and triumphs, Hiroshi continued on to help birth a new form of manga, as the history of the medium unfolded around him…
If you like the art or tone in either of these manga by Yoshihiro Tatsumi, I encourage you to check out the other. A Drifting Life is autobiographical, whereas Good-Bye is a collection of short (fictional) stories, but both will interest you if you're interested in Tatsumi's work, historical manga, or gekiga.
A man returns home limbless, mute, and disfigured after sustaining severe injuries during his service in the Russo-Japanese war. Though she is repulsed by him, his wife does her duty and nurses her husband, attempting to tolerate his sexual appetite and make his cruel life as pleasant as possible. But after a few years this repulsion turns to loathing, and then to abuse, as the woman begins to take out her frustrations and stress on the man...
Many farmers, workers and housewives live eventful lives in pre-modern rural Japan. A man's daughter is being taken advantage of each night by a mysterious spirit, a young boy is intrigued by a mistress's daughter, even though his interest is usually met with a closed fist, and an old woman known as Young Bride is taunted by everyone in her village, amongst other tales.
Two gekiga compilations of stories that tend to be short, end abruptly, or end dismally. Plot-wise they aren't similar (Good-bye focusing on WW2, Red Snow on pre-modern Japan), but they definitely have a similar vibe.
Even those that survived the atomic bombing of Hiroshima couldn't escape its repercussions. Ten years after that fateful day, blast survivors still struggle with lingering radiation exposure and squalid living conditions. During this time, Minami Hirano ignores her worsening physical condition and tries to live her life as best she can, despite being haunted by what she saw and how she reacted during the event. Then, fifty years in the future, the city has been rebuilt and the radiation has subsided, but the ghost of the tragedy still looms in the minds of those that were left behind.
This recommendation especially applies to the first story in each of these books, both of which are about the devastation and after-effects of the nuclear bombing in Hiroshima.
Aside from that, both somberly detail the post-WWII era, refusing to water anything down. Children will undoubtedly find both of these manga very boring and/or incomprehensible.