Mix all the ingredients in a bowl until combined. Taste test, you can add more ketchup/honey for extra sweetness, or oyster sauce/soy sauce for added umami and depth.
Apply it to freshly cooked okonomiyaki with a pastry brush or back of a spoon. Enjoy!
Notes
Taste before you call it done: The bottles you start from are not standardized, so the same measures land differently. Mix, taste off the spoon, and adjust. This is the difference between fine and yours.Do not skip the oyster sauce: It is the easiest one to leave out and the one you miss most. That low savory depth is what stops a homemade blend tasting like sweetened ketchup.Add the honey last and go slow: Ketchup and honey both pull sweet, so it is easy to overshoot into candy. Add the honey in a small pour, stop early, and let it settle.Too sweet, reach for Worcestershire or vinegar: If it lands candy-sweet, stir in a little extra Worcestershire or a few drops of vinegar, a touch at a time, tasting between additions until it balances.Too sharp, soften with honey: If it tastes acidic like straight Worcestershire (common with sharp British bottles), add honey a small spoonful at a time. The sweetness rounds the edge without changing the sauce.