I have a BMI of 23, so I need to diet, right?

I am 188cm and 84kg.
Looking at the numbers alone, it seems fine, but I have a "skinny fat" physique where I'm thin but have a belly..ㅠ
My BMI comes out to 23.
I assume diet control is everything when it comes to belly fat?
There is a limit to losing weight through exercise alone while eating everything I want.
I am in my late 40s.
For those with experience, what method would be best?
I just want to lose about 5kg..