The themes could also include redemption. After kidnapping Marco, Tom might realize the error of his ways and try to make amends. And there could be a theme of friendship. Even though Tom has kidnapped Marco, the story could explore if their friendship can be salvaged.
I'm not sure specifically which 'tom kidnaps marco fanfiction' you are referring to. There could be many different interpretations and stories with such a premise in the fanfiction world. It might involve a complex plot where Tom, for some reason, decides to kidnap Marco. Maybe it's due to jealousy, or a misunderstanding in their relationship within the context of the original story it's based on.
Star would be a likely candidate to rescue Marco. She has strong magical abilities and a deep friendship with Marco. She would stop at nothing to find him and bring him back safely.
It could be an estranged family member with a grudge. Perhaps a relative who feels wronged by Marco's family and decides to take revenge by kidnapping Marco. Or it could be a deranged fan who has an unhealthy obsession with Marco and wants to keep him all to himself.
Some stories might have the theme of unexpected alliances. For example, Marco could form an alliance with another captive or even with one of the kidnapper's minions who has a change of heart. There's also the theme of self - discovery. Through the harrowing experience of being kidnapped, Marco might learn things about himself that he didn't know before, such as his inner strength and resourcefulness.
One possible plot could be that Tom kidnapped Marco out of jealousy. Maybe he saw Marco getting too close to Star and decided to take matters into his own hands. He might take Marco to a far - off dimension where Marco has to figure out a way to escape while also dealing with Tom's insecurities.
A prevalent theme is acceptance. Marco has to accept Tom's devilish nature, and Tom has to accept Marco's human quirks. Also, the theme of adventure often comes up. They go on all sorts of adventures together, which helps strengthen their relationship. In some fanfictions, there's also a theme of self - discovery, as they learn more about themselves through their relationship with each other.
You can start by looking on fanfiction.net. It has a large collection of various fanfictions, and there's a good chance you'll find 'tom hurts marco' fanfiction there. Just use the search bar and type in relevant keywords.
One good 'tom hurts marco fanfiction' could be one where Tom tries to win Star back by causing small troubles for Marco. For example, he might use his demon powers to create minor inconveniences for Marco at school, like making his locker stick or his books disappear. However, in the end, he realizes that this behavior is wrong and they end up making amends.
One common theme is possessiveness. Tom, in his yandere state, is often extremely possessive of Marco. He doesn't want anyone else to be close to Marco and will go to great lengths to keep others away.