The main character could be a young adult who is in a long - term relationship. He's at a point in his life where he wants more excitement and adventure, which he doesn't feel he's getting from his relationship with his girlfriend.
Title: 'Breaking Free from Boredom'. The story could be about a young man, let's call him Tom. Tom has been in a relationship for a while, and when he hears 'break up with your girlfriend i'm bored', it strikes a chord. His relationship has become routine. His girlfriend, Emma, is always so predictable. He decides to break up with her. At first, she's angry and confused. But Tom explains his need for change. After the break - up, Tom travels and has all sorts of new experiences, finally feeling free from the boredom of his old relationship.
One possible plot could be that the narrator realizes they have been in a stagnant relationship with their girlfriend. They start to feel bored because they no longer share common interests. So, they plan a series of conversations to gently break up, while also reflecting on the good times they had. After the break - up, they both learn to pursue their own individual interests and grow as people.
One way is to have a character be influenced by the statement directly. For example, a character named Mark hears it and suddenly re - evaluates his relationship. He might start to notice the lack of excitement and decide to break up with his girlfriend, leading to a whole new set of adventures as he tries to find more interesting things in life.
Perhaps it's a story of self - discovery. Ariana Grande's character in the fanfic realizes she has feelings for someone who is taken. As she tries to persuade him to break up with his girlfriend, she also discovers things about herself, like her own boundaries in love and what she really wants in a relationship. It could be a journey of her growth and understanding of love.
One plot idea could be that Ariana Grande's character is a new girl in town. She meets a guy who is really nice but has a girlfriend. She can't help but fall for him, and she starts dropping hints that he should break up with his girlfriend. The guy is initially resistant but slowly starts to have feelings for Ariana's character too.
It could be an original character created just for this fanfic. Someone who has always dreamed of being a landlord and suddenly gets the chance in the Naruto world.
Vegeta could also be the main character. He has a strong pride and a burning desire to be the strongest. In a 'break through the limit' fanfic, his journey to surpass his own limits and perhaps even overtake Goku could make for an interesting story.
It might be an alien. The alien has unique finger gestures that are part of their communication or technology. The 'I'm watching you' could be from a human's perspective who has just discovered this strange being and is observing their every move, including these finger gestures.
Obviously, Alec and Magnus are the main characters. But new characters could also be introduced. For example, a new Shadowhunter trainee who looks up to Alec and tries to help him get over Magnus. Or a powerful warlock from another dimension who becomes Magnus' friend and tries to show him that there are other options besides Alec. There could also be a seer who predicts that Alec and Magnus are meant to be together and tries to nudge them in the right direction.
The main character could be a loner artist. They are so focused on their art that they don't have time for friends. They might be trying to create a masterpiece that will get them recognized in the art world. For example, they could be a painter who is constantly searching for the perfect scenery to paint or the perfect color combination, and they believe that socializing will only disrupt their creative flow.