WorldCat is the OCLC online catalog. It contains over 43 million records describing library holdings worldwide. You can request any books that NU Library does not have by Interlibrary Loan. You can search Worlcat in Japanese.
WebcatPlus is a union catalog of Japanese university libraries and research institutions maintained by the National Institute of Informatics. WebcatPlus now offers links to digitized materials in NDL's Digital Libray from Meiji Era.