By applying high-pressure H2 to a new fullerene derivative, C63NO2SPh2Py (1), having a 13-membered-ring orifice, 100% incorporation of a H2 molecule into the fullerene cage has been achieved for the first time. This result substantiates the theoretical calculations indicating that the energy barrier required for H2 insertion through an orifice in 1 is considerably lower than that for the previously reported derivative with the largest orifice among open-cage fullerenes synthesized thus far. Upon matrix-assisted laser desorption/ionization mass spectroscopy, the removal of organic addends from the fullerene derivative 1 encapsulating H2 and restoration of the pristine C60 cage, which retains approximately one-third of incorporated H2, have been observed.