not only that, Sekai Kamiki as we known he is resemble with Reiji

and his sister, Mirai i think she is resemble with Aira



also Fumina is resemble with Sei

hair colour only, what i talking is hair style... aiya colour very easy to match only.

fumina's and Sei's passion toward a thing actually more resemble to each other.

Yuuma's character more into shady shady one like China heheeee... i mean "not honest" when Sekai questioning him is he come for his sister...(or just say, tsundere  )

i don't recall Sei got dere dere side   

probably from those early BB SD musha gundam line
something like this except this one is based on double X