The fourth player down is Takehiko Bessho, hall of famer and star pitcher for the Giants.
As near as I can tell the guy below him his Michinori Tsubochi, a hall of fame middle infielder. I'm not 100% sure on this one though.
I think the next guy down is named 'Shibata'. There have been a bunch of Japanese players with that name, but none of them look like a match for a late 1940s pitcher. I might have mis-translated this one.
The next guy is
Hideo Shimizu. He was a pitcher, mostly playing for the Dragons. Sometimes he was good, sometimes he wasn't.
The last player is
Testuharu Kawakami. He was one of the most important figures in the history of Japanese baseball. He was a star first baseman (nicknamed "The God of Batting") for the Giants, from 1938 to 1958. Probably the second or third greatest Japanese first baseman of all time. After that he became Japan's most successful manager, and the most notable advocate of the extremely harsh training and disciplinary program that Japanese baseball is famous for.
The numbers on the back are menko numbers. They don't mean anything. These are menko cards; it's a game (sort of like pogs) where kids throw their cards at piles of other cards on the ground and tried to flip them over. Keeping ones that they managed to flip over. Menko cards often have stuff on them that they thought kids would like: cartoons, rock-paper-scissors symbols, math problems (apparently menko card makers were a bit optimistic about kids' tastes), and really big numbers.
What menko numbers are useful for, from the perspective of a collector, is that in most sets card backs and card fronts are paired, so if you know which menko number corresponds to which player (Gary Engel's book will tell you for a lot of sets) you can identify players based on their menko numbers. For example, Engel says that the card whose back you displayed is "Kyuei Player (generic)".
Given that you've got one of them, it's worth mentioning that some menko cards - especially early ones - don't have specific players on them, but have representative images of a player on a team.
Thanks for sharing these cards, I'd love to see the rest of the lot that you got!