In the show SuperGirl thinks that she will never find a relationship for quite a while. That is with a ton of people.
She feels like it’s hard for her to find a man because of the abilities that she has. After awhile she considers giving up. Giving up is not in her nature.
Eventually she meets this guy from another planet just like her. She tries to change him and have him to become a superhero just like her.
Of course, fighting between them happens because of different view points and of the stubborn personalities. After awhile they start falling in love. Of course, he thinks he is the last one of his kind after what happened to his planet.
In the end, he isn’t the last one of his kind. He figures that out by this evasion. He deals with it with SuperGirl by his side with the closest people that love them. They get through it because of the love that they have for each other.