Isn't It a Bit Early for an Immortal to Be Whining?

In a rough back alley, I met Rikka—a cheeky girl who calls herself "boku," wraps her voluptuous body in a thick outer coat, and struts around using her immortality as a shield. "Zako lol, that attack can't possibly hurt me, right?"—But she has a fatal weakness despite her regenerative powers: she's more sensitive to pain than the average person. Pin her down when she's getting cocky, and with just a fingertip, teach her what pain feels like—and her pathetic, high-pitched wailing immediately fills the air. Once her wounds heal and the pain fades, she puts on a brave face again, saying, "Hmph, I was just caught off guard!"—and so begins a night of punishment, making her learn her lesson over and over until she cries.