Why do they disappear in angel beats?

The characters in Angel Beats! disappear because they are in a special afterlife called the "Afterlife Battlefront" where they are given a chance to confront their unfinished business and find closure. This afterlife is unique in that it allows the deceased to experience emotions and feelings that they may have missed out on in life, and through these experiences, they can finally come to terms with their past and move on.

Here's a breakdown:

* Unfulfilled Desires: The characters in Angel Beats! are all individuals who died with strong regrets, unfulfilled dreams, or unresolved issues. They are trapped in the Afterlife Battlefront because they haven't been able to let go of these things.

* Facing Their Past: The battles and experiences in the Afterlife Battlefront are designed to help them confront these issues. They fight, rebel, and experience a range of emotions in order to break free from their mental chains.

* Finding Peace and Moving On: Once they find closure and acceptance, their "Heaven's Door" opens, signifying that they have completed their journey in the Afterlife Battlefront and are ready to move on to the next stage of their existence.

The disappearance of the characters symbolizes them reaching a state of peace and finally being able to let go of their earthly burdens. It is a hopeful ending, highlighting the possibility of closure and acceptance even in the face of death.