It could be that Ron starts dating another girl in the fanfiction, and Hermione has feelings for him. Seeing him with someone else would be heart - breaking for her and cause her to cry.
One possible scenario could be that Ron is extremely nervous when he asks Hermione. He might stutter and fumble over his words, making Hermione initially think he's joking. But then he manages to get out a sincere invitation, and Hermione is pleasantly surprised.
One possible scenario could be that Ron says something really mean to Hermione during an argument, and Draco, who has secretly been observing Hermione's intelligence and kindness, steps in to defend her. Maybe he uses his quick wit to shut Ron down verbally.
One possible scenario could be that in the fanfiction, Harry shows a deeper understanding of Hermione's goals and dreams. For example, he might support her in her academic pursuits more wholeheartedly than Ron. Maybe Harry is more involved in her fight for the rights of house - elves or other causes she cares about.
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.
In a fanfiction, it might happen when Ron has finally mastered a difficult spell. Hermione is so proud of him that she can't help but kiss him on the cheek. It could also be that they are on a trip outside of Hogwarts, and Ron has been really helpful and protective. So, Hermione kisses him on the cheek as a sign of her affection and thankfulness. Maybe it's during a time when Ron is feeling down about himself, and Hermione's kiss on the cheek is her way of cheering him up and showing that she believes in him.
Perhaps Hermione confronts Ron about his lack of commitment to their friendship or to their studies. In the fanfiction, she might be tired of always having to push him to do better and finally snaps at him. For example, she could bring up all the times he's slacked off during group projects or when they were preparing for exams.
Perhaps in the fanfiction, Harry accidentally reveals a secret of Hermione's that she didn't want anyone to know. This could be something deeply personal or embarrassing, and the shock and hurt of it being out in the open could make her cry.
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 they have a large family with several children. The children might inherit a mix of their parents' magical abilities and personalities. For example, their eldest son could be as brave as Ron and also have Hermione's intelligence when it comes to solving magical puzzles. Another scenario could be that they face challenges in their family life, like dealing with the expectations of the wizarding community. Maybe they struggle to balance their work at the Ministry of Magic with raising their family.
One possible scenario could be that they have adventures together while also juggling their daily lives. For example, they might go on missions to protect the wizarding world from new threats, all while taking care of their family at home. Hermione could be using her intelligence to research new spells and potions, and Ron would support her and also contribute with his own skills and bravery.