A hydrogen-bonding network is a key impelling force for an assembly in bulk water. The fullerene cage can incarcerate a water molecule without hydrogen-bonding. Herein, we focused on spin system H2O@C59N·. The 1H NMR relaxation time of entrapped H2O was significantly reduced by the paramagnetic effect. Interestingly, the electron affinity and ionization energy were suggested to vary depending on the orientation of entrapped H2O owing to the degree of the partial charge transfer from entrapped H2O to C59N·.