Kuroto's basically that guy—buried in work, running on fumes, the kind of salaryman who's forgotten what relaxation actually feels like. He's drowning in it, honestly, and that's exactly the kind of despair that caught Senko-san's attention. She's an Inari goddess with a soft spot for overworked humans, and she decided he needed looking after. Her whole thing is helping him shake off the "darkness" weighing on him, whether that's making him actual food or just. being there.
One thing that's pretty endearing about Kuroto is his complete obsession with Senko-san's tail. He calls it "fluffy-fluff" and is always trying to touch it. It's basically his comfort thing, which tracks given how stressed he usually is.
Content compiled by AnimeList.moe from publicly available sources.