We would like to clarify nature of structural anomaly inside superconducting state in beta-pyrochlore superconductor KOs2O6. In the last experiment, we succeeded to reveal that the structure at 2 K in the superconducting (SC) state is no longer equivalent to that above Tc, while origin of this anomaly remains unsettled due to lack of data between additional first-order transition in the SC state, Tp, and Tc. We propose to continue single crystal neutron diffraction experiments to measure at intermediate temperature at 8.5 K between two transitions. For confirmation, we want to track temperature variation of reflection intensities for several selected reflection as well. This study is indispensable to clarify the nature of the mysterious transition at Tp, and together with the previous one of CsOs2O6, will enable us to deepen understanding on relationship between rattling and superconductivity in AOs2O6.