When a person dies, their soul leaves the body in the form of a butterfly and the body itself rots away quickly after.
The "butterfly" is recorded as data for a person's lifespan. 49 days after the "butterfly" leaves the body, it disappears forever.
The government agency "Death Agency"'s job is to collect, freeze and manage those butterflies before they disappear. Using these managed butterflies, the family of the deceased ones can come in contact with the dead in the form of 3D hologram.