"Gate of shoujo" is where the sprits of those who have been unexpectedly murdered arrive after their death.

she must be gatekeeper of the "Gate of shoujo" (a gate between this world and the afterlife), the destination for all the assassinated people where she will leads the wandering spirits to seek their ultimate path.

Once every month she will have to listens to the tragic tales of murder victims and gives to them three choices:

1. The first is to accept their unreasonable death and go to heaven to be resurrected in their next lives.
2. The second is to refuse their death and wander eternally in the real world as lost spirits.
3. The last is to curse someone in the real world, but in exchange chose to go to hell.

she must be the chosen one, thats why she went missing each month because she needs to take the restless spirits to the real world to discover what lay behind their death in order to help them determine their ultimate path.
the gate keeper needs not eat and they have fantastic healing abilities and the umbrella is actually the tools for her to enter the realms of shoujo. the gatekeeper not only possesse the ability to see the dead, she also can sense death through a vision that will show the last 4 minutes of the victim tragic death in her head. Where she will then use her umbrella to enter the realm of shoujo and wait for the victim's arrival.