"Mam" was something Ryuuko called our mother on her deathbed and it was name some might call their mothers. Of course, our mother was dead and the child she abused so horribly didn't seem to notice her absence. To our little sister, it didn't seem off that someone was absent in our family, as we had been all she had known. However, that being said, I found it odd to find her calling, "Mam? Where Mam?"

Like Nui, Aikurou also found that strange and states, "Well, certainly, she can't be calling for your mother, as she is who Ryuuko's learned to fear the most." He did point it out that he hasn't seen her say the word before except for when she was leaving our dying mother in the hospital, however, he brought up the possibility that she was using "Mam" to refer to someone else.

At first, we didn't know who and Nui suggested our sister created an imaginary mother for herself, to which Aikurou pointed out that it could be a possibility, after all, she did seem to have incorperated imaginary play with her hands and her toys. "Perhaps, she was playing." he suggested, gesturing to Ryuuko playing with her stuffed animals in the other room.

She was playing with her toys for a little while before she stopped and called out, "Mam?" We were intrigued and curious, Nui saying, "Maybe she's seen a ghost." I rebuffed that notion, citing that our mother would have been one terrifying specter and that Rei would have been equally frightening to Ryuuko as the Mistress would have been. A moment of silence passed before she let out another but rather insistant, "Mam!" Aikurou and Nui looked me for answers before the latter went to see what she wanted, which was followed by a brief conversation.

"Ryuuko, are you okay?"

"Where Mam?"

"Ryuuko, she passed away."

"No! Where Mam?"

"Okay..."

"Where Mam? Want Mam, Nuggie."

She walked back into the room and said, "She's not talking about the Mistress. Don't know who her 'Mam' is but I know she isn't talking about the Mistress." We were puzzled and wondered who she could be talking about, to which Aikurou suggested that I go in the room to see what she wants. I shrugged and went to see what she wanted to which I got the response of, "There Mam."

I glanced up for a moment and said, "No, Ryuuko, my name is 'Satsuki', not 'Mam." She looked at me for a moment, as if trying to comprehend what I've said. I was just as confused as I was being called something that isn't my name or, for that matter, title, as I am not her mother. After looking at me, she blinked and said, "There Mam." I opted to remind her again of what my name and title was.

"No, Ryuuko, I'm not 'Mam', I'm Satsuki, your sister, not your mother. Our mother passed away."

"There Mam."

"No, Satsuki is your sister."

"Mam."

"Sister."

"Mam."

"Satsuki is your sister."

"There Mam."

"Satsuki-"

"Mam, you Mam."

Then she smiled, her face lighting up, and clapped her hands, saying, "Mam!" For some odd reason, I was "Mam" to her and, apparently, in her mind, that was a good thing. After Aikurou and Nui walked into the room, I asked the former as to what he thought to which he said, "Hmm, it seems to be that Ryuuko acknowledges you as more than a sister, rather, she sees you as a protector, a maternal figure to substitute for the one had been deprived of. This would make sense seeing as she mostly interacts with you more and has probably observed how some are with their own children, in which case, she internalized that you protect and love her, making you 'Mam', her protector, more so than 'Satsuki', her sister."

He also pointed out the same for Nui, as she didn't say "Nuh-ee" when she acknowledged her, instead she called her, "Nuggie", which was probably intended as an affectionate nickname, as only she could think of. It was odd, however, the explanation made sense, as verbal wise, Ryuuko isn't well versed but she does know how to get her point across, easily.