A third volume hasn't been confirmed.My stand, [SOUL SISTER] will administer justice!!!
But really, this is one of my favorite series, has it really ended?
It's the tulpa's kid. The tulpa sister literally says "I'm gonna have a baby, a girl, if it's born safe I'll find you," but they never meet again. Then the friend says "Yeah, the weird lady looked like you and had a baby girl," the bullied girl made the connection, with "Oh, so my older sister had the kid and she's doing well."What I enjoy is the ambiguity of the ending: "She had a little girl with her. So she was born safely. Yeah. I'm glad she's doing well."
Yes, it could mean the big sister—in fact, that is the most obvious interpretation. But what if it refers to the bully? The bully that also had a little girl? It would be a moment of ambiguity again, like maybe she did do it after all, and this whole tulpa thing is a lie.