Well, a major theme in this type of fanfiction is the exploration of the dark side. The bad boy and bad girl often have a side to them that is not so clean or proper. There's also the theme of power struggle within their relationship. Sometimes they compete with each other, and other times they team up. Another common theme is the search for identity. As they are different from the norm, they are constantly trying to figure out who they are, and their relationship plays a part in that discovery.
One common theme is rebellion. The bad boy and bad girl often rebel against the norms of the ninja society in the Naruto world. For example, they might not follow the traditional training methods or the strict hierarchy of the ninja clans.
One common theme is rebellion. Bad girls and bad boys often go against the norms of society or the rules in their schools or communities. For example, they might skip classes or break curfews. Another theme is the transformation. They start off as 'bad' but through their relationship with each other, they may begin to change for the better or at least understand the importance of certain values. Love against all odds is also common. Their 'bad' reputations make it difficult for them to be together, but they still fight for their relationship.
Rebellion. Both the bad boy and bad girl often rebel against social norms, family expectations or authority figures. For example, they might skip school or go against traditional values. Another theme is passion. Their love is usually intense and passionate, not a calm and ordinary kind of love.
One common theme is the idea of redemption. The bad boy often has a past full of mistakes, and through his relationship with the good girl, he starts to change for the better.
Growth. As they fall in love, the bad boy and bad girl usually grow as characters. In 'Kimi ni Todoke', Sawako, who was seen as an odd girl, and Kazehaya, a popular boy, both grow and learn from their relationship. They change for the better, leaving behind some of their 'bad' traits as they develop a deeper connection.
Conflict is also a major theme. Their personalities, which are often headstrong and independent as 'bad' characters, lead to a lot of clashes at first. However, these conflicts also add spice to their love story as they learn to understand and accept each other over time.
Love against all odds is another theme. Their different personalities and backgrounds create obstacles, but they still fall in love. It makes for a very engaging story as they try to overcome those differences.
One common theme is redemption. The bad boy is usually on a path of self - destruction or causing trouble, and the good girl helps him find a better way. Another theme is the power of kindness. The good girl's kind nature has the ability to break through the bad boy's tough exterior. Also, there's often a theme of transformation, where the bad boy completely changes his behavior and values due to the influence of the good girl.
One common theme is transformation. The bad boy often changes for the better because of the good girl's influence. For example, he might start to care about school or his future. Another theme is the idea of opposites attract. Their different personalities draw them together. The good girl might be drawn to the bad boy's sense of adventure, while the bad boy is attracted to the good girl's kindness.
Love is a very common theme. The bad boy and the girl usually fall in love despite their differences.