I don't get Japanese cup sizes. I've tried to do my research, but for some reason I keep getting distracted...
It's easy; in Japanese manga, the cup sizes ratio, from manga to realism, are:
Manga | Real
AAA . . . infant
AA . . . . 12-year-old
A . . . . . AAA, AA, A
B . . . . . B, BB, C
C . . . . . C, CC, D
D, DD . . E, EE, F, FF
E, EE . . . E, EE, F, G, H, I, J, K, L, M
And, finally:
E - K . . . G-S cup, with no relation to any form of reality
See? Super easy.
(Brought to you by somebody whose wife had a 34DDD in 2000-2001, and has gone up to a 36KK in the last 25 years.)
AFAICT, Japanese cup sizes are completely made up in any manga you read, and should simply be ignored.
And if it advertises the character as being an "A Cup," it's probably
child porn a loli.