So far most of the series has been more focused on Mimi’s development, but while here, the key focus is on Sheena. We have seen Mimi grow to be more than just a weapon. Despite what seemed like a relationship that was more like a mother and daughter in which Sheena reminded Mimi of her mother. As people mention how lucky she is to have Mimi as her partner. We know Sheena wants to stand on her own and not just have Mimi protect her.
Mimi doesn’t want to lose anyone like the case with Seiran. As Mimi can barely remember her mother, the fear that she would forget her one day is terrifying. It’s clear that her feelings for Mimi have evolved from motherly to more romantic. Despite Mimi’s childish demeanor, they are the same age supposedly.