The morning after Mako had brought Nui home, everyone was watching TV in the living room (Nui and the Student Council had slept on the living room floor). Nui had told them everything that happened after her death and resurrection (and noted that the Death Fibers greatly resembled Jack; Jack replied that the Master Of Puppets did sound a bit familiar).
"Hey, Inumuta," asked Nui, "what was in that drink you gave me a few hours ago?"
"A cocktail of antipsychotics and antidepressants," he replied.
"Thanks. I feel better than I have in years."
"So...we're just gonna let her stay here?" asked Ryuko.
"Don't see why not," said Jack, "You let the fuckin' dictator and her merry band of sociopaths live with us, and Nui, however batshit crazy she might be, has only killed one person. Like, I don't want her here any more than you do, but it just seems a little hypocritical in my opinion."
"Jack, she killed my father."
"Yeah, really sorry about that, Ryuko," said Nui, "If it helps, it wasn't my idea."
"Fuck you."
"Ryuko, may I talk to you in private?" asked Satsuki.
They walked upstairs.
"Look, Ryuko, I don't trust her, either."
"Then why do you insist she stay with us?"
"Nui could be a valuable asset. She might be useful against Ragyo and these Death Fibers."
"How do you even know if she's telling the truth?"
"I don't, but I'm not going to ignore a possible threat to humanity. And...Ryuko, she's still our sister."
"Half-sister."
"Ryuko, you know what it's like to be under Ragyo's influence. If you broke free from it, why can't she?"
"...Fine. She can stay. But I'm not happy about it."
They went back downstairs. Shiro and Jack were having a discussion.
"Why can't we take a blood sample from your vomit?"
"...Y'know, I never thought about that. Get me a bucket and some vodka."
Shiro got him a bucket and some vodka. Jack drank the vodka, and vomited a black liquid into the bucket. Shiro went into the bathroom with the bucket and some lab equipment.
"You guys are disgusting," said Nonon.
"Disgusting, but practical," said Uzu.
About half an hour later, Shiro came back with the results. He was visibly disturbed by something.
"Uh, well, I-I have the results. 95% of Jack's DNA is composed of something resembling blue Life Fibers, likely the Death Fibers that Nui told us about."
"That answers the only question I had about what I am. Master Of Puppets probably erased every memory related to him. Since the little psycho we're lettin' live with us mentioned him, I've been startin' to regain my memories about him."
"So...you already know what the other 5% is?"
"I've always known what the other 5% was." Jack drank the rest of the vodka. "Human. The last 5% is human. My full name is Jackson Elias Blackstone, and I am 118 years old. The Master Of Puppets turned me into this in 1927, and he wiped my memory in 1975. He had a codename for me, too. He called me the Thin White Duke."