In this article, we perform a thought experiment about living donor kidney transplantation. If a living kidney donor becomes in need of renal replacement treatment due to dysfunction of the remaining kidney after donation, can the donor ask the recipient to give back the kidney that had been donated? We call this problem organ restitution and discussed it from the ethical viewpoint. Living organ transplantation is a kind of ‘designated donation’ and subsequently has a contract-like character. First, assuming a case (...) in which original donor wishes the return of the organ which had been transplanted into B, and the original recipient agrees, organ restitution will be permissible based on contract-like agreement. However, careful and detailed consideration is necessary to determine whether this leaves no room to question the authenticity of B’s consent. Second, if B offers to give back the organ to A, then B’s act is a supererogatory act, and is praiseworthy and meritorious. Such an offer is a matter of virtue, not obligation. Third, if A wishes B to return the organ, but B does not wish/allow this to happen, it is likely difficult to justify returning the organ to A by violating B’s right to bodily integrity. But B’s refusal to return the donated organ cannot be deemed praiseworthy, because B forgets the great kindness once received from A. Rather than calling this an obligation, we encourage B to consider such virtuous conduct. (shrink)