Although having one odd tyre on your vehicle is less than ideal, unless the tyre is a different size to your existing Michelins it is not illegal. It is however a budget tyre which has clearly been fitted as a cheap replacement due to a puncture or damage on the original Michelin. Given the low mileage we would expect the Michelins to still have plenty of tread left, so we would recommend replacing the Kpatos with a matching Michelin.