Soooo.....
I was thinking that maybe, Aki is also the cat "Master".
I checked the previous chaps and whenever Master is there, Aki isn't and only shows up when Master is away.
That's also why he knows about the psychological thing that Sai mentioned.
I could also be wrong coz they refer Master as a "she"
I remember watching an anime having this same concept. Its like an underground store or black market (something like that) where a beautiful guy sells extra ordinary pets. each customer has their own short story and will teach you about lessons in life..unfortunately i can no longer remember the title. now lets see how the 2nd story will go..
Omg! Finally, an update! Thank you! (づ ̄ ³ ̄)づ