Reimu didn't seem to notice that she had a pin stuck in her hand. Of course, she wouldn't have noticed, as she was conditioned not to notice pain or injuries. However, the physiological aspect of pain stimuli caused her hand to close up, like it would even if she responded, but she was conditioned not respond otherwise. I picked her up, held her in my arms, and gingerly pulled her the pin from her hand, to which it jerked away. The pin was covered in blood and seemed to have been there for awhile, as well as being stuck in there deeply, meaning she had to have crawled on it with her hand and it closed up but her crawling on it, while her hand was balled into a fist, pushed it deeper.
I treated her wound and bandaged her hand, also making it a task to keep sharp objects off of the ground. If she wasn't going to fear anything, then she may as well know what pain is but it would cruel to recondition her to respond to it, since that sort of instict has been removed from her. For someone who didn't respond to pain, she had a habit of hitting or biting someone. Of course, Tenshi had it coming and other times Reimu seems to reserve for wanting to get attention.
"Loser says 'What?'"
"What?"
"Yup, your turn to change Chen's diaper."