One possible scenario could be that it's a moment of extreme stress and they find comfort in each other. Maybe they've just survived a close encounter with death eaters and the emotions are running high.
Harry could be initially shocked but then very happy for them. He might see it as a sign of hope in the midst of all the darkness. Ginny, on the other hand, could be a bit jealous at first, but then come to accept it and even give Hermione some relationship advice.
One popular scenario could be a moment of extreme danger where they think it might be their last chance to express their feelings. For example, in a battle against a powerful dark wizard, they share a kiss as a sign of their unspoken love. Another might be a time - travel plot where they get to see each other in a different light, and the kiss is a result of that new understanding. A third could be a situation where they are forced to pretend to be a couple for a mission, and the pretend relationship turns into real feelings, leading to a kiss.
One interesting scenario could be that it's a moment of extreme relief. Maybe they've just survived a dangerous encounter at Hogwarts and as they're on the train leaving, the emotions are so high that they share a kiss. It's a spontaneous act, out of the joy of being alive and having each other's support.
It can add a new layer of drama. Their relationship change can create conflicts with other characters, like Ron. It might also make the story more interesting as readers get to see a different side of their relationship.
One scenario could be that they are in a life - or - death situation. Maybe they are surrounded by enemies and think they won't make it out alive. In that moment of desperation and realization of their unspoken feelings, they kiss. Another could be in a dream - like sequence where Kakashi has a vision of a different future with Sakura and they kiss in that vision.
Perhaps in a situation where a magical artifact is about to explode and destroy everything around it. Harry, being closer to it, decides to contain the blast instead of letting Hermione get hurt. His selfless act of heroism in this 'harry died for hermione fanfiction' is a way to show his deep bond with her, even if it means sacrificing his own life.
One possible scenario could be after a big argument and making up. Maybe they had a fight over something silly, like Ron being jealous of Hermione spending too much time with a new wizard at Hogwarts. Then, after realizing their mistake, they have a heartfelt moment and share their second kiss.
One possible scenario could be that after the battle, Ron and Hermione are both in a state of relief and joy. They look at each other, and without a word, Ron just leans in and kisses Hermione. It's a moment of pure emotion, a celebration of their survival and their unspoken feelings for each other.
One scenario could be that it's a celebration at Hogwarts. After a big Quidditch victory, a female fan of Harry's runs up and gives him a lipstick kiss on the face. Another could be that it's a part of a school play, and the lead actress, who has a crush on Harry, gives him an unscripted lipstick kiss on the face during the performance, causing chaos and laughter among the students.
In the fanfiction, perhaps Hermione first makes a list of all the characters in the Harry Potter universe who she thinks would be a good match for Harry. She then starts to subtly nudge them towards Harry. For example, she might invite Ginny, Luna, and Cho to a study group with Harry, and gradually, feelings start to develop among them. She could also be the one to smooth out any misunderstandings or rivalries that might occur between the girls vying for Harry's attention.