After the Assasians event, Kasumi will have death on her mind. Enter Eris, with her kindness and concern, to bother comfort Kasumi in her vunerable state. Kasumi's thinking something like "If I were truly dead could I...be with Seiichiro?", and of course Eris is going to grant her wish. Not to be too convient, of course, it's not in Meifuu that Kasumi ends up. Banished to Soul Society, misadventures ensue.

i.e.:
Kasumi-> thinking of death
Eris-> wants to 'help'
Kasumi-> "Could I be with Tatsumi if I were dead?"
Eris-> "Why of course dear. Let's do that."
Kasumi-> Banished to another world. "Oh my. This is not meifuu..."
Eris-> Cackles.
Misadventures in Soul Society ensue.