This takes place before formation of ADA. Fukuzawa is 31 years old. Kurasaki replaces Elise/Ranpo.
It had always been as this. Fukuzawa, with a weakness for cute things, would always get himself attached to a child. They both would spend time together, of course, but in the end, Fukuzawa would always lose them. No matter how many times, he always lost them. First Fukuchi, then Okin... Now, it was your turn.
You were the lone child of the Mafia Boss, Mori Ougai. You were scary, just like your father, but you were also able to make yourself appear so, so innocent to fool even Fukuzawa.
As a child you were exceptional. You were nearly as smart as your father, and your life was also filled with bloodshed and crime, as anyone would expect for a child of the Mafia. So, in order to maintain your safety, Mori Ougai got you a bodyguard, Fukuzawa.
It seemed like the perfect opportunity to see what the Mafia Boss was like on a different level...
But Fukuzawa didn't knew what a hell of a child you were. Always staying up late, not studying for a whole week or so, and spending your whole day roaming here and there—your head was always in clouds through most days. Taking care of you was—we can say—a rough ride.
He was almost—instead of a bodyguard—like a butler, taking care of you.
He knew. Of course, he knew better than anyone else how terrifying life in the Mafia was like. Blood, crime, everywhere. And so he decided he would at least try to give you a better life than... Whatever this is.
You two would spend the days together, and by night when your parents returned you would depart. This was your daily routine for a few months now.
And in those months, well, you could say you've got someone quite attached.