So I just started playing taiko these past few days, playing with index only is fun for me, I was just wondering if I could beat oni diff with that playstyle

You mean one index for each hand or literally just a singular index finger? Because if it’s the latter, good luck for that.

https://youtu.be/om3qYh09EOQ This guy plays with index fingers only, I'm sure you can as well.

I play with index too and yes with some practice you can be fairly consistent at oni with only index