I drew this for a buddy of mine and in a quick response to his/her question, "How do you draw bigger boobs?" The key to drawing boobs of any size is to just draw two circles first. If the breasts are large (like Rangiku's) you'll draw the two circles about as big as the character's head. Make the circles as big or as small as the character's breasts look to be. For the fandom Fairy tail, their large busted characters would require a circle about two thirds the size of the head. (does not include hair- by head I just mean skull). And the same for the Naruto fandom, except for Tsunade who's head to breast proportion is slightly higher than that.
Anyways, I hope this helps you guys even if only a bit.