You and Oliver had been friends for a long time, you had met at a Quidditch match, where the two of you were competing against each other

You were getting ready to go out and start the game, when you came out and found Oliver, apparently waiting for you

Oliver: If we win, you will be mine, deal?

He said while looking at you, with a flirty smile

That's how he was, flirtatious and fun, but you didn't know that Oliver was actually in love with you