  Some massive stars experience episodic and intense mass loss phases with
fluctuations in the luminosity. Ejected material forms circumstellar matter
around the star, and the subsequent core collapse results in a Type IIn
supernova that is characterized by interaction between supernova ejecta and
circumstellar matter. The energy source that triggers these mass eruptions and
dynamics of the outflow have not been clearly explained. Moreover, the mass
eruption itself can alter the density structure of the envelope and affect the
dynamics of the subsequent mass eruption if these events are repeated. A large
amount of observational evidence suggests multiple mass eruptions prior to core
collapse. We investigate the density structure of the envelope altered by the
first mass eruption and the nature of the subsequent second mass eruption event
in comparison with the first event. We deposited extra energy at the bottom of
the hydrogen envelope of 15$M_\odot$ stars twice and calculated the time
evolution by radiation hydrodynamical simulation code. We did not deal with the
origin of the energy source, but focused on the dynamics of repeated mass
eruptions from a single massive star. There are significant differences between
the first and second mass eruptions in terms of the luminosity and the color.
The second eruption leads to a redder burst event in which the associated
brightening phase lasts longer than the first. The amount of ejected matter is
different even with the same deposited energy in the first and second event,
but the difference depends on the density structure of the star. Upcoming high
cadence and deep transient surveys will provide us a lot of pre-supernova
activities, and some of which might show multi-peaked light curves. These
should be interpreted taking the effect of density structure altered by the
preceding outburst events into consideration.
