I have the same issue>feminine jfashion styles
You can start by dropping this and dressing more mature. You don't have to dress matronly, but simple things like ditching bows, wearing more fitted longer skirts and coats and changing shoes really make a difference. I found that combining medium/high-range designer "adult" items (like LV Alma bags, Stuart Weitzman shoes, etc) with "cuter" feminine clothes makes you look more adult and put-together while still maintaining your overall style.
Makeup makes a huge difference too. I found that, contrary to what I thought would happen, bold lipstick (like bright red) makes people mistake me for younger more often. Look at normie western influencers and see what they're doing, sharper arched eyebrows, dark eyeliner especially in the lower lashes or the millennial "cat eye" can age your face quite a bit.