I think master doesn't love Eugene and is using him (i guess to get info from others like in chapter 1 and 4). And i think Eugene doesn't love the master, or not with the conventional type of love. Maybe is obsession, or he feels the master is the only one who "loves" him? or bc the master "saved" him when he was little he thinks he loves the master, idk. Also, in chapter 3 we can see that the pact? or whatever it is, between the master and Eugene, and it did not come to fruition because one of the two did not love the other. In this case it is believed to be because of Eugene, but perhaps it is because of both of them. That's what i got.....
Does Eugene love master? Does master love Eugene? I wonder what the master was thinking when he took in Eugene