We investigate the performance of T2HK in the presence of a light eV scale sterile neutrino. We study in detail its influence in resolving fundamental issues like mass hierarchy, CP-violation (CPV) induced by the standard CP-phase delta13 and new CP-phase delta14, and the octant ambiguity of theta23. We show for the first time in detail that due to the impressive energy reconstruction capabilities of T2HK, the available spectral information plays an important role to enhance the mass hierarchy discovery reach of this experiment in 3ν framework and also to keep it almost intact even in 4ν scheme. This feature is also of the utmost importance in establishing the CPV due to delta14. As far as the sensitivity to CPV due to delta13 is concerned, it does not change much going from 3ν to 4ν case. We also examine the reconstruction capability of the two phases delta13 and delta14, and find that the typical 1σ uncertainty on delta13 (delta14) in T2HK is ∼ 15^0 (30^0). While determining the octant of theta23, we face a complete loss of sensitivity for unfavorable combinations of unknown delta13 and delta14.