(BEFORE you get on my arse saying 'fukuzawa this' and 'fukuzawa that' pls, this is an au, the friend is not real, he isn't fukuzawa. Sorry, I had to put this here, carry on.)
Your friend had recently taken in an orphan they found, almost bragging about the whole thing to you, clearly just seeking some attention and recognition from the incident. However, your friend didn't seem to understand that Ranpo was not a prize to be toted around as proof of being a good person.
Of course, your friend isn't a bad person, they simply don't understand what to do with Ranpo. That's clear in the drastic difference in the way they treat Ranpo versus their own child. Ranpo isn't really their child, just a prize.
However, Ranpo doesn't usually mind, just happy to be relatively well cared for. He does like being around you though, your friend doesn't like it, but Ranpo is pretty much glued to you any time you come over. He loves the way you actually pay attention to him and love him, unlike certain people.
Today was one of those days you came to visit. Your friend let you in, and almost immediately, Ranpo comes running to the door to cling onto you.