It might be an adventure story. The girl could use her disguise to explore new places or get involved in exciting escapades that she wouldn't have been able to otherwise.
There's also 'Twelfth Night' by William Shakespeare. Viola pretends to be a boy named Cesario to work in a strange place. The plot gets quite interesting with all the complications that arise from her disguise.
The most common theme is identity crisis. As the girl pretends to be a boy, she often questions who she really is. Is she still the same girl inside or is she becoming something else? Another theme is the power of disguise. It shows how a simple change in appearance can lead to different opportunities and experiences. And finally, the theme of equality is there. By being able to function as a boy, it shows that girls can be just as capable, which is an important message in these types of fanfictions.
Well, such a manga might explore themes of identity and self-discovery. It could have funny moments when she tries to keep up the act and serious ones when her secret is at risk of being exposed.
One popular 'girl pretends to be a boy' fanfiction is 'The Girl Who Became a Boy for a Day'. In this story, the girl has to pretend to be a boy to enter a male - only competition. It's full of humorous situations as she tries to fit in with the boys, like learning how to walk and talk like them. Another one could be 'Masquerading as a Boy', where the girl disguises herself as a boy to protect her family's honor. The story unfolds with her facing various challenges and making new friends along the way.
In real life, it wasn't common for a rich man to pretend to be poor and chase after a girl, but it might happen in some novels. This kind of novel usually depicted the male protagonist who seemed to be rich at the beginning but lowered his standard of living in order to pursue the female protagonist, even sleeping on the streets to express the male protagonist's sincere feelings and persistent pursuit of love. However, this kind of plot did not appear in all novels because the author would also decide whether to set up such a plot according to the story and the needs of the audience.
It could lead to all sorts of interesting scenarios. Maybe she's trying to hide her past or start a new life.
It could be a love story. The boy and girl are brought together by magic. Maybe the magic makes them see the best in each other and fall in love.
It could be a story of friendship, with the boy and girl supporting each other through various adventures.
It could be a fantasy manga where the main character hides their true strength to avoid unwanted attention or danger.
There are many such stories. One common type is where the girl's personality and inner qualities win the boy over.