I like a lot of Japanese pop music, and my wife, being from there, likes even more of it than I do. And as anyone who's married knows, there's a lot of cross-pollination of tastes - you can't avoid it. After you've been exposed to enough J-pop, you start to realize something: almost every even semi-famous artist there has had work done. Most Americans who are into Japanese music, and even some Japanese themselves, don't realize this. It's far more prevalent than in America.
Please note that I'm not making a moral judgment on plastic surgery itself. What I am saying is that the Japanese are really good at it. They know how to make people look the same, but better. Whereas it seems like most westerners who go through major plastic surgery come out the other side looking like gargoyles (or at best like they've obviously had work done), in Japan it's usually very hard to tell unless you knew what the person looked like before. Even then, it's often not obvious what procedures they've actually gone through. I've been following certain artists long enough to notice this. In some cases, the artist will eventually confirm the surgery; in other cases, they'll keep it a secret.
First, two really obvious and famous cases, both confirmed by the artists themselves:
Both Ayumi Hamasaki and Kumi Koda had obvious eye jobs at the very least (Kumi Koda also had an obvious nose job). The "roll" below the eye is removed, a more obvious crease is given to the upper eyelid and in general the appearance of the eye is enlarged and tightened up. It's kind of a myth among people who have heard about Asian "eye jobs" that the goal is to try to look more "western"; if anything, it's the opposite. You can see here that it made these two artists have noticeably bigger and less tired-looking but definitely still Asian eyes. They almost look like anime characters. Regular people in Japan don't have eyes like Ayumi Hamasaki's - almost anyone you see with eyes like that had an eye job. That includes almost every "idol" and famous pop star. This is now an extremely common procedure; it's like getting Lasik.
This is Nozomi Tsuji, who I believe falls in the unconfirmed category, but it's a pretty obvious (and almost extreme) case if you ask me. She basically went right for the maximum eye size up to - but IMO, not beyond - the line that separates "cute" and "freak". If you get it right, you get maximum cuteness, but oh, how easy it is to step over that line. She looked like the "after" photo in the first photos after her maternity - so she had a bit of a break when nobody was taking pictures of her. In her case, she was actually popular before the eye job, so a lot of people did notice and talk about it when she came back.
Now a couple of "did she or didn't she?" cases:
That's Maki Goto both when she was in Morning Musume and now. She had a confirmed eye job before that first photo. But compare it with the next couple. Is it just age? Makeup? Lighting? You could make the case either way. The thing is, it's actually only been a few years, whereas to me the first and second photos, at least, look 20 years apart. When I saw these recent photos of her after not following her for several years, I didn't even recognize her.
When I see them side by side with her old self, her facial features look basically the same, but I still feel like there's something different. I can't put my finger on what. People don't change that much in just a few years, once they're an adult (she was already 18 in the "before" photo). She seems to have done something to tone up the sexiness and tone down the cuteness. Given her previous history, it wouldn't surprise me if she had more work done, even another eye job. (Though it's true that eyeliner can do amazing things.)
This is actually what inspired me to write this post. That's Haruna Ono of Scandal. I never realized how different she looked in their early stuff until I bought their "Video Action" BD, which has a couple of videos from their indie days that I hadn't seen before. The difference in the videos is actually a lot more pronounced than in these photos (this is just all I could find on the net). Check it out yourself - here's one of their very early videos, and here's a later one to compare it to. In the "before" photo above, that's her second from left. Something is different, isn't it? Her face used to be rounder and flatter. She's much more attractive now.
If she did have work done, it was very early - the suspicious thing is that she looked suddenly very different in their first "official" video for Doll, and has looked basically the same ever since. "Doll" was shot literally only a few months after that first one I linked above. It could just be styling or aging, but it could be something else. She was already 20 in that "before" photo, and she's just 23 now - so her aging shouldn't make a big difference. I didn't find anything online that told me for sure one way or another.
It's not just girls that go under the knife:
That's Gackt, formerly of Malice Mizer and now of... himself, I guess. This is another case where it's hard to see exactly what was done but most Japanese generally agree that he's had some work. His eyes definitely look different, and his entire face is thinner and more defined (and no, he doesn't appear to have otherwise lost weight - he was always this thin). Maybe some cheekbone and jaw work? I'm not sure if Gackt himself has ever confirmed it, but the guy is such a prankster and con artist that nobody takes anything he says seriously... meaning even if he said he'd done it outright, it'd probably convince more people of the opposite.
In all of these cases, most people I've talked to agree that the artists in question look better than they did before, although the differences are so subtle that a lot of people don't seem to notice it until they look back at some old pictures or footage. Then they have that "wait... what?" moment.
I'm sure you could find cases where the opposite is true and the work done was not an improvement, but certain procedures are so common in Japan now that they're almost pre-requisites for having a singing career. If you suddenly notice a famous person from there becoming a lot more attractive when you never noticed them before, you can almost be assured that it's not just makeup.