I don’t know if there’s a complete collection anywhere, but here’s a Shincho Monthly article that has some of it (obviously NSFW): archive.org/details/erotica_of_osamu_tezuka
Most of it is transformation fetish stuff, ranging from human->anthro stuff to weirder inanimate and body-horror-esque/“what-has-science-done” kinda transformation art. Tbh I kinda wonder how much of it was really fetish fuel and how much of it was artistic musings. Some of the drawings are so bizarre that it’s hard to believe that they’d actually trigger someone’s fetish and seem more like he was just exploring surreal transformations.
Then again, I’ve been exposed to a lot of obviously pornographic art that normies would think was too weird to be fetish material, so I’m probably mistaken.