Small breasts are larger than a flat chest and smaller than medium breasts. In real-world sizes, this can run from just over AA cup to just under C cup. If that seems large, just remember:
Breasts in anime art defy biology, physics, and common sense. [...] these tags don't make sense when you try to apply them to living people. They're made for two-dimensional teenage heroines for whom anything less than double-Ds is on the small side. - iridescent slime
Use this tag if:
Lower bound:
The character's chest is not flat
Upper bound:
The breast would not hang over a hand placed immediately beneath the breast
In other words, if there's enough to cast a shadow, yet there is not enough to hang or squeeze together, then use the small breasts tag.
