You find some fingers from long ago. They must have been set aside by their previous owners. They definitely weren't cut off or anything, someone just decided they didn't want them anymore and set them aside.
I know why they set aside their fingers long ago, it's because there was no soap (そ). If you didn't have soap to clean your fingers you wouldn't want to keep them for very long...
Currently there are no similar looking kanji which exist in the WaniKani learning system