After seeing what is sister had done while she had the Journal of Facts in her hands, and since he was inexplicably unable to erase it, (when he tried to strike what his sister had written and drawn, his work instantly disappeared, letting her words and drawing intact) Colin decided to lock said Journal in his room and explain the truth about it to the only person that would believe him: Aditi.
If anyone else had claimed the old notebook was able to rewrite reality, the Râkshasa slave would have deemed them ripe for the madhouse. But while she wasn't able to read his mind, the link between her and Colin let them know the mental state of each other. Aditi could feel how her master felt scared and panicked, but no sign of him loosing his mind. This combined with the faint feeling of power emanating from the book made her perfectly willing to believe him.
Normally, with everything he said on the subject, she wouldn't come near the thing if she could help it, especially since it was believed to have changed her species by creating a new one and having turned her into a slave, but the Journal of Facts was already influencing her.
That night, Aditi couldn't sleep. Getting up, she came from her room to Colin's, taking care to not make any sound, took the Journal of Facts, and got back to her room.
The young Râkshasa wanted to use the Journal of fact to insert someone that would help her with her insecurities regarding the romantic side of her relationship with Colin but, naturally, said Journal was about to screw things up.
Aditi wrote that while she was in the hands of the madman that had enslaved her and made her a guinea pig, there was a mermaid, a siren to be precise, that took her under her wing, so to speak, protecting her as much as she could as a fellow slave. Her name is Undine Thelxinoé and when Colin was added to the wizard's slaves, he too ended under her protection.
Mermaid being long lived creatures, Undine was among the the slaves that had known multiple masters, and the evil wizard had enough time with her to use her in multiple experiment. Honestly, the fact she's still alive and well is a miracle. One of said experiment was to give her the ability to transform, a bit similarly to Râkshasas and Wulvers, so she could turn her tail into legs and live on earth. (Part of a plan to make some sort of super-soldiers, which was part of a greater plan to conquer the world. The usual.) The experiment had worked, but costed her the ability to have kids, making her care for Aditi and Colin like they were her own.
Undine is a young adult which, being a siren, mean that from a human point of view she was born generations ago. She have long red hairs, green eyes, F-cup breasts, a sexy and very pronounced hourglass figure and a tail the same color as her hairs. Unless she's in her human form, in which case she have long slender and sexy legs. Even her voice exult feminity, on top of its hypnotic quality making her able to ply anyone except her master to her will. (That said, she can still use it to help her master stay calm, if necessary.)
Being a slave for so long, the ‘young’ siren couldn't be freed from her status as a slave. She too, like Aditi, ended up in Colin's care, acting as a nanny for him and his slave Râkshasa.
As Aditi closed the Journal of Facts, she believed she only took it by curiosity, wondering if, being Colin's slave, she could see what was written in it, but clearly Colin was the only one who could. Again she silently infiltrated her master's bedroom to deposit back the Journal, hopping he wouldn't know she had taken it.
Undine surprised her going out of Colin's room. Aditi instantly pretended she had a nightmare and needed to see that their master was well with her own eyes, regardless of what her link with him said. The siren instantly believed it. The same thing had frequently happened when they first came here after all, and still happened form time to time. In fact, the mermaid was up for the exact same reason.
Meanwhile, the Journal of Facts was gleeful. It may not have pulled the same trick as he did with Jane, not sure if Aditi was any good at drawing. But it made her write everything two times, so Colin wouldn't be able to erase her changes, or even be aware of it. In fact, it may be better that way, making things even more confuse for the young human. Did he already have a siren slave named Undine Thelxinoé who was like a second mother to him? Or was her existence somehow a secondary effect of Aditi becoming a Râkshasa and his slave?