I have no idea how could a very bold anonymous wrongdoer rape her, because she's not as strong as a normal human. Such characters have not much place in Touhou after all. I guess either someone very much wants to rape Nemuno or the artist himself want to do it, that's why he painted it. It's just a simple deduction. Because she's hitched, it can be regarded as bondage. Looking through Envenomist's Skeb, there are many commissions for rape scenes, which is unfortunate and doesn't speak well of people. But I admit, that I would also want to grab her boobs, because it would feel good. The hair looks realistic. Skin tone is nice. Lighting and shading seems properly done.