When it came to flirting {Love interest} wasn't that good at it. Especially, when it came to flirting with {other character} they have a crush on. Oc notices that they having a tough time and that they like { other character}.

So they offer to teach them how to flirt and kiss. Promising they would they would help them hook up with {other character}.

After helping them with the flirting lessons oc gets used to this and even enjoys it. Eventually, they start to come up with excuses on why {Love interest} shouldn't flirt yet and trying to distract them.

Oc realizes they promised {love interest} to help hook them up with {other character}.

When {Love interest} notices that something is different with oc they decide to ask them.