IDE Library is available without reservation for visiting from April 1, 2025. You will be able to access to the second floor and above.
Please see below for details.
https://www.ide.go.jp/English/Library.html

The Library of Economics, the University of Tokyo has a mutual use agreement between the IDE library. Registered users of the Library of Economics can borrow books as an individual at the IDE library.
Please see below for the necessary procedures.
https://www.lib.e.u-tokyo.ac.jp/?page_id=5746 (in Japanese)