Just dropping in to recommend this insanely high quality animation I found recently. There's a ton of fetishes in it that I don't have (Giantess, Insertion/Unbirth, Absorption, Vore, Feet), but I still found it very enjoyable personally.
https://www.pornhub.com/view_video.p...=64aafcb8336a5
If you're looking for the breast expansion it starts at around minute 8 until the end.