Responses

*They're. [they ARE the only couple...] "their" is used as a possessive pronoun, meaning it belongs to them [their relationship is special]. "there" is an adverb of place [there is nobody like them]. An article like "the only" can't follow their*... (●'◡'●)ノ . Sorry to grammar nazi your correction, which wasn't a correction at all... <3
I love the way they first meet and tsumabuki might be right that they're the only couple who meet in the unusual way ╮( ̄▽ ̄)╭