Nightfall is a nice and caring unicorn, but one day he does a big mistake. He cheats on his loved one, Blue Light, and he really regrets it. But it is not always easy to get things back to normal when you've done wrong and in times like this, good friends are a blessing.
And if somepony wonders why it's tagged with "sex", it's not a clopfic so keep your pants on. Just "some things of sexual nature" ^.^