Luka us just very tall ╮(￣▽￣)╭
It’s not that he is built as a child it’s just that Japanese guys are not super tall. Also the tribe that Luka is in has a bunch of really tall people due to their diets and yes that tribe is real. The tribes are also known for their Masai jump because they can jump very high. So a regular Japanese high schooler (Also Makoto’s dad said Makoto had anemia before because he doesn’t eat a lot and your diet is one of the reason for you height) with a teenager who drinks goat blood and has a very healthy diet are reasonings behind their height and body. Also if you see videos of Japanese guys in high school they really aren’t buff they’re more on the skinnier side unless if they workout.
Mako is built like a fucking child lmfao