Kira is not fit enough to be Alice. She is a psychotic bitch.
Suigintou is incomplete. And she killed Boku.
Main character becoming Alice would be too cliche. So, no Shinku.
Kanaria is too childish.
Sou and Hina are dead.
So, who is left to be Alice?
The doll that never would hurt her sisters. The doll that is not incomplete. The doll that is the most popular character in the series. The doll that is love.
None other than Suiseiseki.