Peni Peni is the yukkuri equivalent to the penis. It acts like (and superficially resembles) a real penis, but it injects a type of bean paste which is different from normal bean paste, because it can impregnate another yukkuri (from a different species, except for Yukkuri Rinnosuke. Attempts by a yukkuri to inseminate another of the same species inevitably fail without external "assistance") either by contact or by injection. Peni Peni only appears in some stories and drawings. Others using different methods of reproduction.