Twilight Sparkle had always been close to Princess Celestia but from past actions and lingering feelings they had drifted apart. Princess Luna's only companion was her sister Tia but with a thousand years separating them, she feels uneasy and unsure, even if determined. Princess of Friendship and ruler of Ponyville royal duty was to make sure all of Equestrian ponies were happy and learning friendship, with a nudge from Celestia, Twilight starts to teach Luna, the magic of friendship.
Elements of harmony and friends of Twilight Sparkle need their own help with friendship as they deepen into something more. Twilight might be teaching others of love, friendship and communications but her friends will show her how to accept it for herself.