For sure, any pro athlete is likely on something. But it was just for showing that even with a real training (not those stupid training promoted by gurus), a muscular ass isn't huge. It fits the body.But those are professional fit girls (fighters for what I see) who work for WWE, so I'm 95% sure they use anabolic substances. I'm not gonna say that the 2019 Maria Nagai is the fittest girl but to me it's pretty obvious she hit the gym and that her ass is natural.
I've seen a lot of "fatty" jav girls, even idols who are skinnier than (2019) Nagai and when the weight gain is only fat it's pretty obvious.
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So I downloaded the same movie lol, and yeah, there, it looks good, so before the implants and her fat gain. But I'm not sure about how her workout affected that. I would need her real training plan to judge haha. Still, she probably just did "legs" as her upper body has nothing, no upper back development to balance the lower body. That's typical of "fit girls" on instagram tho (reason I ignore those girls)
unfortunately, she went crazy and ruined her body after that