[3] Their impoverished family previously lived in one of Gwangju's shantytowns, before relocating to North Jeolla Province's Gochang, in South Korea's countryside, in 2010, after his father, a construction worker, suffered from serious injuries.

[7] However, at the 2014 Artistic Gymnastics World Championships in Nanning, China, he fell on both of his vaults—the first for which it was announced in Nanning that he was widely expected but failed to receive naming credit for a brand new top then 6.4 difficulty vault, initially dubbed the Yang Hak Seon 2, or a straight Tsukahara with 3½ twist—failing to defend his title and finished in seventh place with a final average combined score of 14.416 after qualifying in first place.

At the 2017 Artistic Gymnastics World Championships in Montreal, Canada, Yang had "qualified" (Q) in first place for the vault event final but pulled out after that because he had sustained a hamstring injury during qualifications.

At the 2019 Artistic Gymnastics World Championships in Stuttgart, Germany, Yang had qualified for the individual vault event final in first place, but finished eighth after falling out of the first vault—his own the Yang Hak Seon on vault, or front handspring (layout) triple twist—as well as incurring a 0.300 penalty for stepping out-of-bounds because of that.

Yang's training and preparation for the 2020 Summer Olympics in Tokyo, Japan, were adjusted for his performance to peak accordingly for one year due to 2019–20 COVID-19 pandemic.

In the 2021 Artistic Gymnastics World Championships in Kitakyushu, Japan, Yang qualified for the individual vault apparatus finals in a tie for the highest average combined score of 14.833 with but ranked second to Nazar Chepurnyi of Ukraine after the tie-breaking procedure was applied.