Anime/B

Bl

 * Black Clover:
 * Bleach: From episode 343 (where The Lost Substitute Shinigami arc starts), Riruka Dokugamine appears, which has the ability ("fullbring") to shrink objects.

Bo

 * Bobobo-bo Bo-bobo - EP??:
 * Boruto: Naruto Next Generation - EP057: During a "ninja tournament-exam", Chōchō Akimichi uses "Multi-Size Technique" to become an absolute giantess (maybe standard giantess).

Br

 * Brigadoon: Marin & Melan - EP21: Moe Kisaragi, the best friend of the protagonist, has grown to a giant size, she then tries to be stopped by the army, but continues to grow more in the process.

Bu

 * Burst Speed 3 - EP11: "Flying Chips". It's a Chinese anime and it is originally known as "爆裂飞车3". The are 3 moments: The first moment, a female protagonist is shrunk because she step on a mushroom that it shrinks her, later she interacts with a para-giantess antagonist; the second moment, the same female protagonist grows in size because she stepped on a magical mushroom, interacting with a normal-sized female antagonist; the third moment, all the main protagonists eat the "grow mushroom" and two of the female protagonist become perfect giantesses.