Yukkuri Hosting Service
Because yukkuris are popular pets but difficult to keep alive, Mister and many other people use an internet “Yukkuri Hosting Service,” where the service will house and care for a yukkuri just for you that you can watch and communicate with via webcam.
Mister has a baby Reimu with the hosting service, and gradually the story reveals that he is abusing his Reimu in subtle ways to avoid running afoul of the Terms of Service. (There are other hosting services that cater to abusers, but Mister says they cost too much).
Although he can see and hear Reimu, she only gets to hear his voice, so if he doesn't speak, he can make her desperately lonely by seeming to ignore her.
Users can upload music for their yukkuri to listen to, so he plays video game music that puts her on edge and makes her unable to sleep afterwards.
Users can pay for various extras for their yukkuris like toys, decorated living spaces (options include “Forest Home Type,” “City-Sect Coordinate,” and “Cozy Cardboard House”), special foods, and regular TV viewing privileges. Naturally, baby Reimu lives in a stark, undecorated cell, and he provided her with only the bare minimum of toys to relieve her stress--a yukkuri Marisa doll and a small ball which are now worn from overuse.
When he does give Reimu a “treat,” he orders adult yukkuri food for her (which is tasty, but so hard she exhausts herself chewing it) or uploads a video of a happy yukkuri family in the wild for her to watch, which makes Reimu cry from loneliness.
Meanwhile, Mister also has a pet gold-badge Marisa--a real pet, in his house, that he loves and cherishes. The baby Reimu at the Yukkuri Hosting Service is only an outlet to relieve his stress.