Sakura Chiyono O

A kind and pure-hearted Umamusume. Commonly referred to as "Chiyo" in game and by fans, she may be unremarkable compared to some of her peers, but her determination is nothing to scoff at. She has a tendency to fill out proverbs that she calls "Chiyonotes" in her notebook, though they are indecipherable to others.

[Spoiler] Sakura Chiyono O was named after the professional sumo wrestler Chiyonofuji Mitsugu. He was considered one of the greatest yokozuna in history, winning 31 championships at the top level. His nickname was "The Wolf", which explains Sakura Chiyono O's dog like design in the series [/Spoiler]

[Spoiler] The real life Chiyono O was the son of Maruzensky, explaining their bond in the series. Chiyono O was the first of his lineage to win the Japanese Derby in 1988, something not even Maruzensky had accomplished. Unfortunately, he failed to win a single race after the Derby and retired in 1989 to become a breeding stallion. Sakura Chiyono O would later pass away in 2012. [/Spoiler]

(Source: Umamusume Wiki)