Six-Star Return Gem

The crystal-clear orb, a source of the purest power from the Astral, can return Senshi to a Level 6 state without Divinization or Sublimation.

It can be given to Senshi through the "Give Gift" button in the Senshi interface, and after giving, the Senshi will revert to Six-Star.
You must have a Senshi of Six-Star or higher to give, and regardless of the star level, it will revert to Six-Star and some items will be returned.