Well, in some fanfictions, Harry might comfort Tonks by simply being there for her. He could listen to her problems, like if she's worried about her family or the situation in the wizarding world. Just his presence can be a source of comfort.
One common theme is friendship. It shows how deep and meaningful a friendship can be between Harry and Tonks. Another theme could be healing, as Harry helps Tonks heal from emotional wounds.
Well, her possessiveness might isolate Harry in a way. He may feel smothered by her actions, which could cause him to rebel or try to distance himself. This creates a new dynamic in the story where Harry's actions are influenced by trying to break free from Tonks' possessive hold, and this can lead to all sorts of plot developments like him making unwise decisions on his own or seeking out other allies who are more understanding.
In many fanfictions, Harry might comfort Hermione by simply being there for her. He could sit quietly beside her while she's upset, offering his silent support. Maybe he'll hold her hand gently to let her know she's not alone.
Another way Snape could comfort Harry is by standing up for him in certain situations. Maybe when other teachers or students are being unfair to Harry, Snape steps in and defends him. This act of protection can be a great source of comfort for Harry, as it shows that someone is on his side even if they have had a rocky relationship in the past.
Ginny Weasley could be another character. Given her relationship with Harry in the original series, in the fanfiction she might be part of the harem, bringing her own strong - willed and talented self into the mix, and her experience with the Weasley family's magic and values could influence the group.
One of the main characters would likely be Lupin. Since he has a connection with Tonks, his presence could add a lot of drama to the story. He might suspect their relationship or even accidentally discover it. Another could be Hermione. She's always observant and might pick up on the signs of their relationship, and could either support them or be concerned about the implications. Ron could also be in the mix, perhaps being a bit clueless at first but then getting involved in some way.
In this fanfiction, Harry could comfort Ginny through his words. He might tell her that what happened in the Chamber was not her fault. He could share his own experiences of facing difficult situations and how he overcame them, making Ginny feel that she too can get through this tough time. For example, he could say something like 'I've been through a lot of scary things too, Ginny, and we've always come out stronger in the end.'
He might offer her a warm drink like tea. Tea can have a soothing effect and help with cramps.
Fleur and Tonks might start off a bit wary of each other. Fleur, with her proud and somewhat haughty nature, could see Tonks as a bit too brash. But as they both love Harry, they would have to find common ground. They could start sharing stories about Harry's heroic deeds from their different perspectives. Eventually, they would become friends and support each other in the relationship with Harry.
One possible reason could be that she sees Harry as a symbol of hope in the wizarding world. As a hero figure, Tonks might feel the need to protect and be possessive of him to ensure his safety for the greater good.