  We perform one-dimensional radiation-hydrodynamic simulations of energetic
supernova ejecta colliding with a massive circumstellar medium (CSM) aiming at
explaining SN 2016aps, likely the brightest supernova observed to date. SN
2016aps was a superluminous Type-IIn SN, which released as much as $\gtrsim
5\times 10^{51}$ erg of thermal radiation. Our results suggest that the
multi-band light curve of SN 2016aps is well explained by the collision of a
$30\ M_\odot$ SN ejecta with the explosion energy of $10^{52}$ erg and a
$\simeq 8\ M_\odot$ wind-like CSM with the outer radius of $10^{16}$ cm, i.e.,
a hypernova explosion embedded in a massive CSM. This finding indicates that
very massive stars with initial masses larger than $40\ M_\odot$, which
supposedly produce highly energetic SNe, occasionally eject their hydrogen-rich
envelopes shortly before the core-collapse. We suggest that the pulsational
pair-instability SNe may provide a natural explanation for the massive CSM and
the energetic explosion. We also provide the relations between the peak
luminosity, the radiated energy, and the rise time for interacting SNe with the
kinetic energy of $10^{52}$ erg, which can be used for interpreting SN
2016aps-like objects in future surveys.
