極上の貧乳 ぺったんこ 大平原の小さな胸 無乳 ナイチチ 平らな胸 ツルペタ つるぺた
For Danbooru purposes, a flat chest is exactly what it says, i.e. no breasts whatsoever. For breasts larger than flat yet smaller than normal, use the small breasts tag.
Primarily for use with older-looking characters, though it may also be applied to loli characters. Not for use with child depictions.
This tag may be used for otoko no ko characters where appropriate, although puffy chest may also be appropriate.
The flat chest tag is mutually exclusive to the breasts tag, i.e. don't tag both unless another character in the picture meets the criteria for the breasts tag.
The following tags are aliased to this tag: titty_buds, tsurupeta, flatchest, pettanko, flat_chested (learn more).
The following tags implicate this tag: flat_chest_grab (learn more).