If we do end up leaving Kei behind she and Snowflake are going to have the most interesting conversations as I suspect Snowflake would follow Hazou to the ends of the earth whereas Kei would feel too trapped by her obligations.
Hazou would send a Shadow Clone to convince Kei to come with him as that is a thing Hazou-the-traitor would most likely do and Kei would summon Snowflake to better assess such a dire choice. Snowflake would be convinced to go with Hazou but Kei would come to a dawning, horrible icy logical conclusion that she absolutely must stay in Leaf as her skills are not strictly needed in rift research, but they can make a difference if she stays.
Can you imagine the self-loathing levels Kei will experience as every time Snowflake gets dispersed Kei receives all of the creative reasons and motivations as to why she should have left everything behind to go with Hazou? The despair Snowflake will feel as every time she exists she knows her duration isn't long enough to find Hazou and that her subservient existence chains not just her, but her ability to follow her heart's desires in ways she can never break free from?
Kei and Snowflake might just approach hitherto unprecedented levels of tragedy.