If you're looking for manga similar to Ashita no Joe: Fighting for Tomorrow, you might like these titles.
The story centers around the life of a young boxer named Ryuuji Takane and his sister Kiku, who is his coach. Ryuuji and his sister both inherited their father's talent for boxing with Ryuuji inheriting his strength and techniques while Kiku picked up his talent for analysis and strategy. In the past, their father was a famous boxer. Ryuuji and Kiku went away from home to train and become famous in order to help their lonely mother. On the way to stardom, they have to defeat the strongest challengers all over the world.
Umeboshi Kinya lives only for the sole purpose to fight and become stronger. But since he became the king of the baston, nobody dares to be measured. Kinya So bored and depressed ... It takes the hair of the beast and heard talk of a potential adversary that it will be a pleasure to go cause! He landed in a boxing hall where it does not happen as it really would have thought ... So? Who is the strongest now?!
Horiguchi Genki was a 5-year-old boy. His mother died when he was born, and he was raised only by his father. His father, Shark Horiguchi, was a professional boxer, but he was ruined and became an itinerant boxer. However, Genki believed his father was strong and he would become a champion, and he had a dream to become a strong boxer just like his father. After his father’s death, he was adopted by his grandparents. Although they opposed Genki boxing, Genki made up his mind to become a boxer, and he continued training secretly, by meeting with various people.