It does what it sets out to do very effectively, which is disturb you. It takes a severely depraved mind to come up this type of content. I understand it's an art form, and I can respect it in that aspect, but that's all the respect I can give. I don't regret watching Shoujo Tsubaki, but I can't recommend it. There is one specific scene that the movie could have gone without, and I think it the main reason why I dislike the movie. Without spoiling it, I'll just say it involves dogs.
Overall, if you want to watch it, go ahead. Would I recommend? Not in a million years.