>>11705943Which of those girls do you go out of your way to watch? Whoever you instinctively reach for is your oshi, i'd say.
You can also have more than one oshi with a leaning towards one.
There's no real rule to being a fan of vtubers or anything, but something like getting a favorite happens naturally.
The oshis that actually stuck with me even to this day were the ones I didn't even have to think about.
The ones I put more than 1 minute thought into never lasted for more than a couple days at best until they were replaced with another girl.
Maybe you're having problems because those girls aren't actually oshi material to you.