The Soul-Catchers by Naoko Higashi

What if you could come back after death to watch over your loved one, installing yourself in a treasured mug, for example, or perhaps your mother's hearing aid, a diary, or even a climbing frame, to feel the clambering limbs of a beloved sister? Eleven recently deceased protagonists find themselves floating in the afterlife where a nameless ghost offers them a joyous reunion with their loved ones. But not as you would expect.