I am not sure if the above manga has been translated into english, but I bought the first volume in chinese at my local manga store.
In an alternate feudal era (or so I think), females with huge breasts are respected, while those with flat chests are scorned. Chibusa, who belongs to a ninja clan high in the caste system, escapes with a scroll containing the techniques of improving a female's bust size, intent on changing the current societal system. Along the way, she has to battle assassins hired by her clan, partake in "breast-related festivals", and learn the greater secrets hidden within the manual.
Chibusa has the uncanny ability of reducing a buxom woman into one with a flat chest, simply by cutting her opponents, without causing any wounds to their bodies. At the same time, Chibusa's bust increases whenever she uses this unique ability.
Personally, I found the storyline to be wacky, most probably drawn and created by an mangaka with a fetish for breasts. And with breasts, you can expect lots of frontal nudity though I have yet to see any explicit sex scenes as of now. If you like breasts to a great extent, then Manyuu Hikenchou will definitely cater to your tastes.
Cover of the first volume:
Figurine of Chibusa that is already on sale: