It is novel about a one-tailed fox from the demon realm who gains a system I think and transmigrates to different worlds and saves the cannonfodder character. In the first Arc it saves the cannon fodder high school student. It gains points from the system for saving the cannon fodder and with that points it grows new tails to finally become a nine tailed fox. I think in the first or second arc it becomes a movie star. And also it doesn't change into human form in both arcs. The cannon fodders in those worlds mistake it for a pomeranian at first instead of a fox.
Hi. The novel who touched my tail is yaoi but the novel I'm referring to is not yaoi. But thanks for suggesting I might read the that novel later.
In that novel the MC Transmigrates into a human I think but in this novel doesn't change into a human it is still a fox.
Sorry, I just took your description and googled that. First thing that popped up. The only other one I know is 'I Am That Little Fox'.