When making the glassy water-ionic liquid, N,N-diethyl-N-methyl-N-(2-methoxyethyl) ammonium tetrafluoroborate [DEME][BF4] solution, the water molecule existing as a single molecule without self-associated state is preserved even at 77 K and survives not to form the hydrogen bond network among themselves as in pure H2O liquid. The water molecule might loosely interact with BF4- anions: At water-rich concentration, H2O ice crystals and the water molecules in the ionic liquid coexist as a mixture, which may result from microheterogeneities in the solid aqueous ionic liquid solution.