While I do agree that these types of manga serve some type of copium due to the largely humiliating defeat that Japan suffered in WW2. Japan was NOT vastly inferior regarding technology compared to the US or Europe at the time of WW2.
Japan being technologically inferior might have been true during the last stages of WW2 in 1944-1945 but that was because their nation has already been blockaded, bombed many times, starved, and lacking resources to make any type of technological advancements. However during the early years of WW2 Japan was one of the leading technological nations in the world.
For example the Zero Fighter was one of first and most advance monoplane fighters fielded by any air force at the time, the US didn't even have any fighter that can match the performance of the Zero in 41 to early43. Zero Fighter was only matched with the arrival of the US Hellcat Fighter in 1943. Also while the US and Europeans were still unable to choose between the battleship or carrier as the flagship of the navy at the start of WW2, the Japanese have already perfected their carrier fleet operations. Why do you think the US was unable to stop the attack on Pearl Harbor? Because the US didn't even think a coordinated carrier attack over very long distances between Japan and Hawaii was possible, showing that Japan at the start of WW2 was more advanced than the US regarding carrier operations. Lastly, while battleships were slowly being replaced Japan still built the Yamato and Musashi, 2 battleships that were larger and more technologically advanced than any battleship ever built by Europeans or the US at the start of WW2. Only the Fast battleship Iowa Class from the US was able to match it, which was only commissioned in 1943. Showing that Japan also had the edge in battleship technology in early WW2.
TLDR version: Japan lost NOT because being technologically inferior. Infact most Japanese technology were on par or even ahead compared to some of their US/European counterparts. Japan simply lost because of manpower, size, resources.
I am sorry but you are incorrect in some cases.(wall of text incoming)
For instance Whilst the Zero fighter was more maneuverable and was able to climb at higher rates, it did so by sacrificing their fuselage and self-sealing fuel tanks aka Agility over durability. So it's more of a compromise than "advancement" in tech, furthermore there are cases where their agility and speed was overcome through effective tactics(but I don't count tactics as technology mind you) , for example in the coral sea battle in may 1942 where F4F Wildcats achieved quite the favorable kill ratio over the Zero fighters.
As for the Yamato and Mushashi, come on, they were not "advanced" their advantages only lied in the equation of "bigger equals better" Their Guns where the largest ever mounted on a ship at the time, and their armor was thicker (and obviously they were the largest battle-ships ever built).
But they had huge disadvantages that U.S and European navy vehicles didn't have.
For example the U.S Navy had far superior radar-directed fire control systems allowing them to accurately engage enemies at longer distances and in poor visibility. The Yamato class ships relied heavily on optical rangefinders that were less effective (bordering the ineffective)in bad weather or at night.
Then we got the Yamato anti-aircraft defenses, Again the U.S and British had radar-guided AA systems the Yamato class ships didn't have, and the American 5"/38 caliber guns with proximity-fuzed shells were far more effective at destroying aircraft than the Japanese AA weapons.
Then we got the speed and maneuverability, where the Japanese went the exact opposite direction than they did with the Zero fighter. With the Yamato class battleships they sacrificed speed and maneuverability in favor of armor and larger guns.
All in all they were decent but not really technologically advanced since they fell behind in radar, speed, and fire control making them inferior in practical combat effectiveness compared to U.S. and British battleships.
The only point I will concede was the one about Japanese having perfected carrier fleet operations, but still, that's not a technological breakthrough but rather a tactical/training one. As we can see the "empire" in this manga, have also perfected their own naval and "carrier fleet operations"(such as they are), but they still lost to overwhelming firepower and technology.
Finally when I speak about technology I don't only mean in weapons development, but also their manufacturing capabilities(Japanese were reportedly quite inferior to that of the mass-production methods U.S had)
For example between 1940-1945 the Japanese more or less managed to produce approximately 10939 Zero fighters.
Respectively in the U.S they produced ~15,000 units of P-51 Mustang, ~12,275 units of F6F Hellcat,~12,571 units of F4U Corsair, and ~15,660 units P-47 Thunderbolt. That's `55,506 units, easily five times more than Japan could produce, something that U.S population/workforce numerical superiority(that was a little less than double that of Japan's) can't account for.
So, I can safely say that the Japanese bit off more than then could chew thinking that they have technological and military superiority. Don't you agree?