this is Monochrome Tentacle Insertion / Coming out Styles on PonyXL

It can also be used in color, although the style will be lost.

Triggers
tentacles - general use
greyscale, monochrome, line art - use in monochrome generation (keep on art style)
nipple penetration, tentacle insert nipple - tentacle insert into breast from nipple

tentacle out of nipple - tentacle coming out inside of breast