This image was drawn entirely freehand, in pen, with no guide lines. That's why it looks a bit "sketchy". If I had planned it I would probably have used a journal-type book with no lines on the paper. But that's all right, because these are just layouts and studies, not "finished pages".
Breasts are important to otaku. (Guy-type otaku, anyway.) In Japan, most women don't have large breasts. The Japanese diet isn't nearly as high in fat as the American diet is--lots of rice and fish will do that--and Japanese kids average around two hours of PE per day. That's why the Japanese populace in general is so skinny--they start out that way and pretty much stay that way for life.
The girls, however, burn off all the calories which would go into the formation of breasts; this is why they tend to have smaller breasts. I think this is also why Japanese girls tend to skip gym class during their "monthly visit", by the way; they have to. A girl fainting from "anemia" is such a common circumstance in anime that it's a common plot device. (Not to mention that the skin-tight gym shorts they wear probably leave no room for sanitary napkins.)
So, when it comes to cartoons, the Japanese tend to give them breasts--breasts they probably wouldn't actually have.
As for Megumi-chan, as you can see the bustiness of the character is more pronounced here. Well, having seen Yumi-chan in Chobits I realized that I can get away with not making the bustiness obvious at all times. Heck, for being an E-cup, Yumi-chan's character design doesn't seem to have much bust to it.
Ifurita would easily be an E-cup--an American E-cup, if such things exist, which I don't even know. If her measurements match those of Dolly Parton (not an unreasonable assumption) Ifurita's chest would be 40DD. Find pictures of Dolly on the Internet. From the neck down, that's what Ifurita would look like in real life.
To be honest, extra-large breasts seem like a bad adaptation to me. Only humans can get away with it; other mammals don't have breasts unless they're actively lactating. Our closest cousins in the primate world don't even have them; only us. (Well, our females.)
But even so I would think that there would be a certain maximum size above which the things become more of a hindrance than a help, due to weight distribution, resource demands (ie food and oxygen), and so on. It seems that the disadvantages of very large breasts would outweigh the increased breeding opportunities that they would bring.
Hey, human men are wired to like them. Bigger breasts means better survivability for the children--oh, I know it doesn't really mean that, not even in the proverbial wild, but it's the same as with other factors: they're visual cues, not 100% logical and accurate information. Nature lies all the damn time.
In the "wild" the woman with bigger breasts looks healthier and more apt to generate viable offspring. A women with small or no breasts does not.
Given that, though, what about a woman like Dolly Parton? Do the breasts get her more mates? Or do they slow her down so much that she becomes a meat snack for a cave bear before she can breed?
Anyway, drawing large breasts can be problematic. Look at some comic books (American superhero comics, I mean) and look at some of the women in them. I have seen character designs that were completely outlandish: a female character with F-cup-sized breasts (which could defy gravity) and a waist that would be thick on anyone with a smaller chest. OR, worse, an optimum-size waist, which makes the breasts look gargantuan.
In Azumanga Daioh, the character Sakaki-san has large breasts--I note here that I borrowed the last name for Megumi-chan in my little comic because of this--to the point that other characters frequently remarked on it. When she's in her school uniform, they draw her a bit on the thick-waisted side. In swimwear she has normal proportions, though.
There is a sub-genre of Japanese comics in which the female characters are all drawn with extra-huge breasts--breasts that make Dolly Parton's look average. It's called BB, and I'll let you figure out for yourself what those letters stand for. BB manga is supposed to be sexy (it's a kind of hentai, or "adult only", comics) but the enormous breasts just look awful to me. Another evolutionary disadvantage to extra-huge breasts: after a certain size they begin to look disgusting.
And then the latter case leads us to another problem: if you're drawing a nude, how big do you make the aroleas and nipples? If you proportion them to the size of the breast, well, no baby would ever be able to use the things for their intended purpose. But if you draw them a proper size, they're dwarfed by the mass of the things. I guess this is another case where "logic" need not apply.... Fortunately, I don't often draw nudes, and none of my characters have outlandish proportions anyway.
In my collection of "How To Draw Manga" books, the one on drawing female characters devotes several pages to breasts of all sizes, and includes tips on how to show them interacting with their environment. In general this series of books has helped my ability to draw immeasurably--when I need to see how to do something I can just look it up and try the technique out, and more often than not the book pays for itself after one or two episodes like this.
Drawing in General
I was talking to a coworker, the other day, about my drawing skills.
It took me several years to progress to the point that I felt comfortable trying to draw an actual story. For decades my drawings were confined largely to stick figures, and I did some pretty funny stories using them; but after getting hooked on anime and manga, I decided it would be neat to be able to generate some manga of my own. I started trying to draw it in 1995, and struggled and struggled until I hit on the idea of tracing some images. That broke the logjam and I was suddenly able to draw faces. Then I started working on bodies; and after a couple of "How To Draw" sessions at AnimeIowa '97-'98, I started work on the first "finished" pages of American Dawn, the manga series I'd started thinking about 'way back in 1995. I finished several pages before taking a drawing course in 1999, and that helped a lot, too.
Back when I was in junior high, a friend of mine--Mike Indovina, the creator of Satyr and Chimera (http://members.aol.com/chimera900/Chimerapage.html) among other things*, and a graduate of the Kubert school--he was showing me and a mutual friend of ours how to draw. It looked like too much work to me, so I never really bothered with it. Ah, the foolishness of youth.
Anyway, so I started down the comic art path late. But the pages I was doing weren't all that bad--amateurish and somewhat primitive, yes, but not bad. In the intervening time my artwork has improved the same way it has since this started, in bursts: I'll go along drawing something, bing bing bing, and then--whoa! THAT'S how you're supposed to do it!--and it gets a bit better.
It's almost like I'm throwing skill points into my "Craft: Comics" skill....
I started drawing American Dawn layout pages in an unlined, hard-bound journal. These "layout" pages were, for all practical purposes, finished pages, needing only some extra detail and inking to be complete. (And screentones, if I had a source for them.) They look good, even to me (I am my own harshest critic). I carried the practice over to Magical Angel Selene but I have only a few pages of that, in any form, and a stack of studies and character designs.
Stephen Bennett--the guy who was the head of "Studio Ironcat" before it folded, and who worked as an animator in Japan on such projects as Urusei Yatsura--he held some "how to draw" seminars at the various iterations of AnimeIowa and I attended every one, and actually learned something about artwork from him. He advised me that my page layout was too static, that it needed to be more dynamic--and I took his advice and generated two or three pages of Magical Angel Selene which he said were better than the first ones I'd shown him. Anyway, MAS has stalled due to a problem I have.
Bennett says that the two key attributes to a successful artist are PATIENCE and DISCIPLINE. It takes time to learn to draw, and it takes time to draw. And it's not something you can just pick up; you have to practice until your hands hurt--and practice more!--until you learn how to do it. Patience and discipline!
My problem is I can't really draw male characters all that well. I know what Steve would say: "Practice!" but I just don't. I don't because I don't like drawing guys. I like drawing the cute girls.
There is a story that Steve tells at each drawing and cel-painting workshop he gives, about his entry into the world of animation--how his mentor told him to draw Shutarou Mendou, from UY, 1000 times, and how he had a red pen and would draw an X through every drawing that wasn't worthy. His mentor made Steve draw his least-favorite character and would not tolerate so much as one out-of-place line; and finally Steve learned the lessons of patience and discipline...and that was when the real art lessons began.
Like Steve, I like to draw the cute girls, but I don't like drawing the other stuff. It's my biggest failing. So when it comes to a story like Magical Angel Selene, in which the main character is a guy (who transforms into a magical girl--go figure), I have trouble. The main character, Chuck, has two male friends and one female friend...and I stalled because I had to draw the male friends. (And his coach.)
The worst-looking character design in American Dawn is Asa-chan's middle-aged physics teacher, Dr. Heisenberg...because he's bald. I just don't have the patience to draw him correctly. *sigh*
So anyway, I don't stick with my comics. They languish for months at a time. I'm that way with all my creative efforts, and always have been; life intervenes and I do other things for a while. When I come back, my drawing skills have rusted and lost their edge.
But after a while--especially if something inspires me--the skills come back to me; all I have to do is draw for a while and I remember how to do it again. I guess that's lucky.
*--Other things, like the Purple Brute