I see clear differences in shape and size. Everyone IS smaller in the UE5 version, but not in a pure "reduce by X percent" manner. Ayane's left breast for example goes out a bit further in the UE5 screenshot, but there's different detail on her cleavage and skin compared to the original. It also seems to have a softer curve or "drop" in its overall shape. At the same time, it's not just a breast size reduction, all the female characters seem like they were made slimmer all over.
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Note the shoulder and thigh contours.
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Note the shoulders again. On the other hand, the shading on the cleavage is more intense in the UE5 version, and while this is a video screenshot, Irene's breasts actually jiggle HARDER and FURTHER in the UE5 version. Pay attention to the facial expressions too. It seems like with Sega's handling of Yakuza Kiwami 1 and 2, Team Ninja just did some art passes (Like subdividing the models and then making everyone smaller to reduce the need for cleanup) that were heavily assisted by their available software and just let the engine do the rest. This was the case for what appeared to be Lollipop Chainsaw RePop's being censored.
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Similar size, but the breasts "jitter" more in the original version. It seems like in the UE5 version, when the chest moves, it MOVES, but softer motions are more dampened, while the opposite is true for the Xbox version.