Matching tyres

[va1o]

Bought a used car then got home and realised one of the rear tyres is a different manufacturer (Kumho) to the others. I want to replace it so it matches, but it feels a bit reckless throwing away a basically brand new tyre because its slightly different to the others. I'm assuming it's there because the original got a puncture or something. All 4 have good tread so won't need properly replacing for a while. Thoughts?