Well, there could be a bunch of reasons. Maybe the guy has some unique traits that draw her in. Or perhaps they share common interests and hobbies that create a connection. Also, it might be his kindness and compassion that make her obsessed.
It could be that the art style and emotional depth of girl manga appeal to him. Also, some guy might be interested in understanding different perspectives and experiences through such manga.
Maybe it's because manga offers unique stories and characters that she can't find elsewhere.
They're popular because it's a very relatable concept. Many people have had a crush on someone and felt that sense of obsession at some point. It's also a bit of a fantasy for some, seeing someone be so dedicated to another person.
One such manga could be 'Love Beyond Size'. It shows a guy who is head over heels for a chubby girl, depicting their unique relationship.
Perhaps the obsessed guy has a change of heart. He realizes his actions are wrong and lets the girl go. But this ending often comes with a complex set of emotions and consequences for both characters as they try to make sense of what has happened.
Well, often in these stories, the guy starts as a bit of a stalker - not in a creepy way though. He'll find out her daily routine and 'accidentally' bump into her a lot. Then there's the plot where he saves the girl from some sort of trouble, which makes her see him in a new light. Also, there's the scenario where the guy writes her love letters or poems to express his obsession in a more romantic way.
There are many such anime comics. One example could be 'Magical Girl Ore' where a male character transforms into a magical girl. The transformation often brings unexpected plot developments and comical situations.
It might trigger a new plotline or reveal something about the characters' relationships. Maybe it causes a misunderstanding or leads to a heartwarming interaction.
Maybe she's feeling tired or seeking comfort. It could just be a spontaneous act of affection.
Often, the theme of rescue is present. It could be the girl trying to rescue herself or her friends and family attempting to rescue her. Also, there can be a theme of psychological manipulation as the obsessed guy may use various tactics to control the girl.