@LegoBaka
5 confirmed victims we know of before JtT vanished (and there is some historical evidence that suggests that they had been active for longer than recorded, had more victims then we know of, and potentially fled to America at some point) so they could add some of the theoretical information to boost his abilities and power.
@me474
It's a tournament style battle manga written and made by the japanese. Do you complain how there is only ever Japanese protagonists in other manga as well? Out of humanity's 13 Combatants, only 4 are Japanese. If all 4 win then you can claim there is a bias (and even then it would be expected considering where the manga is being made in)
Humanity would have lost the first two battles and won the third regardless of who the author put. It's a simple storytelling style in order to build tension and ensure the audience is actually invested in the manga and rooting for humanity to win by ensuring they actually see themselves as the underdogs against literal gods.
The humans might be from the best known countries that are common for a japanese person to study in school, but the gods are a bit more diverse or are you not going to point out how most of the pantheons being featured for the fights are Greek and Norse, the two most popular mythologies to take from? 5 of the gods in the list are Greek after all.
Either way, it's wrong to label the manga racist when so far we have had 3 battles where the only clear bias so far is that the gods are being heralded as superior to humans and a favoritism towards the Greek pantheon. If by the end the Japanese combatant secure 4 of the 7 wins needed for victory then you can say the manga is somewhat biased, but not racist.
My guess is we wont know for sure until they get down to the last of each side. Manga like this will drum up expense by making them tough and close fights so my guess is humanity is going to win this particular fight.