First published in 1934, Tank Tankuro was one of the most famous manga characters during the time, lining up next to Norakuro. He is said to be one of the first roboto ever to appear in Japanese manga and may be the first superhero in manga. He fights villain, Kuro Kabuto, who attacks Japan, and this Kuro Kabuto is famous among Japanese SF fans that it has resemblance to Darth Vader of Star Wars. Tank Tankuro influenced greatly, many manga artists, such as Shigeru Sugiura, Osamu Tezuka, Fujiko Fujio, etc., and is the foundation stone from which many masterpieces of manga art would spring from. Tank Tankuro became the archetype for various Japanese manga heroes that were to follow. This work is famous for its innovative and captivating adventure stories full of surrealism, nonsense, innocence, absurdity, and eccentricity.
Tank Tankuro is what we call now part of the genesis of manga. While it's a long understanding of western manga fans that the beginning of 'modern manga' is Osamu Tezuka, this isn't exactly true.
Japan had a long history of works resembling manga before the 20th century. Woodblock booklets appeared as early as the 1700's, containing a series of pictures depicting a simple tale, usually historical or legend based. Near the 19th century, more adult tales sometimes with dialogue or narration starting appearing. This was the seed for manga as we know it today.
Gajo Sakamoto's Tank Tankuro is what we would now call manga,
because of two factors; it was paper based, and it had a simplistic unique art style visually different from other mediums. This art style itself was influenced by multiple experimental animated works, and other manga progressives such as Tagawa Suihou. It was an art style purposefully simplified for ease of drawing, and so children of young ages could appreciate it.
As such Tank Tankuro is absolutely a work aimed at young children, being based on an already built tradition of works for those less capable at reading. The story thus, is based on a brawling Tank, fashioned in a odd egg shape with holes. A kind of children's toy visually itself. This Tank has repeated battles with bad guys, unfortunately represented as Chinese (though not concretely stated it's pretty obvious the nationalist themes Sakamoto presents) and has the ability to summon seemingly anything out of those aforementioned holes, and say transform into a plane. It's extremely simplistic, not exactly the most engaging or esoterically pleasing of mangas. Its value, quite honestly, is almost entirely contextual.
The actual manga can be bought in a English hard-copy, which includes several well written essays on pre-war manga- though it is pricey I admit. Perhaps if you see it in a shop, read it while browsing.
I can't recommend this is a manga on its own; it is entirely based at young children who cannot read, it's vulgar and has objectionable political messages, and it simply hasn't grown out of being a novelty. But I can recommend this as a piece of history. Tezuka himself was influenced by different pre-war manga after his initial goal on viewing of the national war movie Momotaro Umi no Shinpei, as were many others. Sazae-san also takes influence, and that's Japan's most popular anime today by far. So, have a read of Tank Tankuro if you're interested in the history of manga, it's extremely interesting for what it is. I can't guarantee you will enjoy it, but undoubtedly you will appreciate it.