If Masayuki Hisada's BeautyCamera could make someone in a portrait appear more beautiful, he would be on to something. The app really doesn't enhance "face, eye, lip," as Hisada says in his app description in the App Store. I'll give him the benefit of doubt and say that something got lost in translation.
What BeautyCamera really does is remove or add to the contrast in a photograph, thus making images appear sharper or softer.
There's more to it than that —BeautyCamera removes or adds color to lighten and darken areas as well. There's no help file, either in the app or on the dev's Web site, so honestly, I can't tell you exactly what's going on under the hood of BeautyCamera merely looking at the results.
Take a look at the photos, with the settings set at both extremes and in the middle and you'll get a better idea of what I'm talking about.
BeautyCamera is certainly easy enough to use. Snap a close-up head shot of your subject from within the app, or import one from from your Camera Roll. Then, scoot the slider left to remove colors and lighten contrast and right to darken colors and the contrast between light and dark.
Next, tap the Update icon in the lower right corner and your results take effect. Unfortunately, there's no way to preview the results before you update, so this is hit or miss, at least until you become very familiar with BeautyCamera's settings.
There is, however, a before and after mode that enables you to compare the original image with the updated one. That's hardly useful frankly.
It would be better to be able to adjust the slider, do a before and after comparison, and then choose to do the update. As it is now, BeautyCamera functions in reverse, thus making it of little use, especially compared to the many other photo apps that do pretty much the same thing.