It could be a plot twist to add drama. Maybe they had to leave for some secret reason related to their feelings.
It could be that the character disappears because of external forces beyond their control after falling in love. Or perhaps they have a personal issue that causes them to run away from the relationship. It all depends on the context and the author's creativity.
I'm not sure exactly what happens in that chapter. You might need to read it to find out for sure!
It could be a tale of self-discovery for the girl. She might learn to see beyond appearances and find true love in an unexpected place. And the monster might change for the better because of her love. However, it might not be all smooth sailing as they deal with the reactions of the people around them.
When the manga rock tyrant falls in love, it might cause chaos in his usual tough world. He could struggle to balance his power and newfound emotions, or it could make his enemies take advantage of his changed state.
It could lead to all sorts of interesting and unexpected developments. Maybe the parasite brings out new emotions or challenges for the boy.
It could result in the assassin changing their ways or finding a way to get out of the assassination job to be with the target. It adds a lot of tension and emotional depth to the manga.
It could lead to a lot of drama and complications. Maybe the teacher tries to resist because it's inappropriate, or there could be opposition from others.
It could lead to a big change in her behavior and attitude. Maybe she becomes more gentle and caring.
It could lead to all sorts of drama and challenges. Maybe the demon has to face opposition from its own kind or the human world.
It can lead to a complex and unexpected storyline. Maybe the bully realizes their mistake and tries to change for the better to win the victim's heart.
Often, when a shoujo manga girl falls in love first, she'll go through a range of emotions. She might become extra self-conscious, try to get the guy's attention, and have all kinds of fantasies about their future together. It can lead to all sorts of cute and sometimes dramatic situations!