Basically, the reason he isn't beautiful like the rest of his family is due to acclimation to the atmosphere of the worlds and the nature of hyumans--their bodies have adapted over time to REQUIRE mana during pregnancy to develop the fetus. After his parents came over, their podies needed time to acclimate to Earth's atmosphere (or how mana works on Earth? I don't recall what exact wording was used). Unfortunately, this process takes multiple YEARS.
- His older sister was born pretty soon after his parents came over (I don't recall if it gets specified, but she may have been conceived in the Hyuman world.
- At that point, his mother had not acclimated to Earth at all--his older sister is effectively fully hyuman (his mother had enough residual mana to make up for the lack of mana on Earth).
- He was born at least a year after that
- His mother was in the middle of acclimating to Earth--which had major consequences for Makoto in his youth
- His younger sister was born at least a year after he was
- By the time she was born, his mother had completely acclimated to Earth--his sister is as close to human as a hyuman can get (and needed no mana during development like humans).
(Transferred heroes can use hyuman magic because of the goddess' personal blessings on them.)
That partial acclimation royally screwed up his development in the womb--it's why he's "ugly" (for a full-blooded hyuman) and it's why his magic was messed up and had to be altered by that human healing magic user (if you don't remember this flashback from earlier in the manga, she had to completely sever his connection to some of the elements to keep him from constantly being near-death).
HOWEVER, that is ALSO the source of his power--the reason he was so weak as a child was because he was essentially mana-starved, which spurred his magic power to grow. He was weak and tired because his body was subconsciously using ALL of the mana around him CONSTANTLY to desperately try to make up for the lack of mana while he was in the womb.
