It could be a shy Hufflepuff student who has been observing Harry for a long time. This student might have some special powers or knowledge that they keep hidden. They become Harry's secret friend because they are afraid of being bullied or judged if their abilities are known.
The 'A Bad Friend' manhwa's main plot centers around the ups and downs of friendship. It follows the characters as they encounter various situations that reveal the true nature of their friendships and force them to make tough choices.
The 'secret crush manhwa side story' could potentially focus on different aspects of the main story. It might take a minor character from the main manhwa and build a story around them. For example, if there was a character who was always in the background observing the main characters' secret crushes, this side story could be about their own unspoken feelings. It could also delve deeper into the cultural or social context that shapes these secret crushes in the manhwa world, like how the characters' surroundings and the values of their society influence their feelings and actions related to their crushes.
The main plot of 'A Secret Between Us' manhwa centers around a hidden truth that binds the main characters. This secret causes them to face conflicts, make difficult choices, and navigate through a web of emotions and complications in their lives.
I don't have enough information to tell you the exact main characters in this side story. It could be the same main characters from the original manhwa, or it might introduce new ones.