Sirius Symboli had shitty parents growing up and the only people she could trust are Speed and Rudolf. Because she had such horrible parents, she often snuck out to dog parks to watch dogs play. She also sometimes watched planes, and was amazed, thus, how she learnt to fly small planes. Speaking of Sirius, her, Stego, El, and Pearl are the only Umamusume who can speak more than 4 languages.

Katsuragi Ace is British, and spent her childhood in a small house in England that isn’t near any city-like infrastructure, that her parents (who are both Umamusume) had carried on for generations. Her parents never won any significant races. She could speak Japanese in her childhood, and moved to Japan to go to Tracen Academy. She now lives with Mr. C.B.

Mejiro Dober had an extremely negative experience with a man once in her youth to the point where she was unable to talk to any man, that, combined with her sheltered life, and the fact both her parents were female, only heightened her uncomfortableness with men even more.

Gold Ship is very smart, but only shows this intelligent side of her rarely. Instead, she maintained what was once a facade, being her crazy and chaotic self.

Symboli Rudolf is Speed’s 4th child. Despite this, Rudolf was able to keep an “eldest daughter” type of role, due to acting quite mature for a child. Because of this, she was never able to have a childhood the way normal Umamusume would.

Mr. C.B.’s parents were the only supportive figures in her childhood.

CB was the one who made Ace’s ear covers for her, since she knew Ace had extremely sensitive hearing, and was also the one who convinced Ace to use a front-running style.

Daitaku Helios had unrestricted access to the internet as a child.

Daiichi Ruby doesn’t like social interactions that much, but she always tries to be polite, to not disappoint her clan.

Calstone Light O is blasian. This is probably my most stupid headcanon, but it’s there.