Charge-density level structure was determined in a prototypical nanoporous material with strong guest-host interaction, K 0.34 Co͓Fe͑CN͒ 6 ͔ 0.75 · zH 2 O͑z = 3.6 and 2.7͒. We determined atomic coordinates and occupancies ͑g͒ of three kinds of oxygen sites of guest waters, i.e., zeolite water, ligand water, and off-axis water, as a function of z. The variation in g against z indicates easily removable nature of the zeolite and off-axis waters, and robust coordination bond with the ligand water. Significant change in the charge density of the host-NC-Fe-CN-Co-NC-Fe-CN-lattice revealed hybridization effect between the off-axis water and the adjacent Co atom.