Nezumicon

A mouse boy with no past and no home talks his way into a servant's job at a mansion full of cat girls, which raises the obvious question of what use he can possibly be to any of them. The story leans into that gap between how small he is and how much still ends up turning on what he does.

It plays out as a kinetic novel, so there's no branching to steer, just the routes of the mansion's residents unfolding one after another as the household's affections and appetites sort themselves out around him. New routes and illustrations get added over time, extending the women he ends up entangled with rather than reworking what's already there.