So, for this crossover I imagine Harry eventually paired with wither Leon or Dylas, but with what I have so far, literally anyone would also be ok, I just wanted Harry to be in the Rune Factory 4 world. I just used the easiest reason for how he ended up here suddenly, sorry not sorry. Credit for "The Veil of Death leads to other worlds" goes to whatever fanfiction author first came up with that idea. Also this is pretty divergent from both the Harry Potter canon and the Rune Factory 4 plot since Harry saves Venti.
Harry will arrive after the protagonist shows up.
He will be a prisoner of the Sects and the protagonist will save him right at the start of the second half of the game, right before they go to the Sects Territory. Both Dylas and Leon will have already been saved and will have been living in the town. Lets say it's the female protagonist just because I'm more familiar with her personality.
So Freya saves Harry, who is pretty badly injured (he had just defeated Voldemort and the ministry immediately arrested him and threw him through the Veil, but not before all his supposed friends – those that survived anyway – accused him of being a murderer and a monster, etc. That's why Harry didn't have the strength to save himself, but he also has no motivation to continue living anyway), so she teleports them to the town, thankfully Vishnal and Volkanon were there so they could help get Harry to the Doctor (Harry had passed out by now).
He spends about a week in a mini coma, Freya coming by every day to check on him, and even some of the other towns people. When he finally wakes up, it's the middle of the night so he's alone. He gets up and wanders around before ending up being drawn to Venti because of her magic. He can feel that something has changed about his own magic and could practically see the magic leaking out of Venti, so he subconsciously started feeding her some of his. He sat near her, his back to the wall, his legs drawn up and resting his head on his crossed arms, giving Venti strength through the night, so that when he woke up in the morning, she was slightly conscious and was speaking to a crowd of people who were all gathered around. Harry, wary about all the people in the room, tensed and prepared to sneak away, when the dragon looked his way, which brought everyone's attention to him.
"There you are! We've been looking all over for you! What are you doing out of bed, you were so badly injured, you've been asleep for almost a week!" Freya scolded gently, walking over to him and getting down on her knees, a delicate hand raised to check his temperature.
Harry's eyes had widened as she spoke and came towards him and he made an aborted move to jerk away from her when she knelt down, but ended up flinching because his body was sore from sleeping in such an uncomfortable position. Freya had froze when she saw that he was afraid of her and watched him sadly as he collected himself. When he was looking at her again, his green, green gaze cautious and empty, she slowly reached out her hand again and felt his forehead.
She was unable to contain herself when she felt how hot he was, "Oh my god, you're burning up! It's no wonder, if you slept here like that while still recovering! What were you thinking?!" she exclaimed in a soft but scolding voice, mindful not to startle him again. The others had either left or gathered around, Vishnal, Arthur, Dylas, Leon, and Doug having stayed, with the Doctor and Nancy standing back near Venti, who had fallen back asleep.
Harry warily eyed everyone in the room before he settled on looking at the dragon. He flicked his eyes uncertainly back to the girl who had been scolding him and remained quiet, just shaking his head gently before looking down, his breathing raged and strained.
She sighed and looked over her shoulder at the others, "We need to get him back to the clinic, will one of you – ?" she was cut off when Harry grabbed her arm to get her attention. He jerked away again when she whipped around to look at him in surprise. Some of the guys had taken a step or two forward when he grabbed her, but she held up a hand, her gaze steady on the mysterious young man who had yet to speak.
"What is it?" she asked quietly. There was a long pause, she thought he wouldn't answer when, "The…dragon…" he started, his voice was quiet and broken sounding, rough from all the sleeping and dry from the fever.
"Venti? She'll be alright, we were actually working on curing her when we found you. Is that why you came here? To see Venti?" Freya asked, surprised that he spoke and concerned for his health.
"No…I could…feel her? She…needed energy, so…I shared…" he trailed off, his vision going out of focus as he swayed violently. Freya reached out to steady him and his head fell forward onto her shoulder. She made a startled sound in the back of her throat but before she could do anything else, Vishnal had come forward and was gently gathering the young man in his arms. As they all stood up, he spoke once more, his voice even fainter and it sounded like it was taking a lot of energy to speak, he said "stay…near" before he finally passed out.
Freya and Vishnal shared a look, before she questioningly asked if there were any other spare beds in the building so he could stay here, near Venti. Volkner and the Doctor immediately tried to protest, but Freya cut them off, "No, this young man has been through a lot, and if I understand correctly, has been sharing his own power with Venti to help alleviate some of her pain! He doesn't even know her, or own her anything, and he was so badly hurt and in no condition to be exerting himself like that, but he did anyway, and all he asked for in return is to stay near, so if it's possible, I want to fulfill his request. Now, if there are no spare beds then put him in my bed and I can stay at the inn – " she was cut off again by Vishnal, "That won't be necessary, Princess, he may have my bed for now." He said, moving towards his room. Freya beamed at him before turning back to the others.
"Will you be okay visiting him here Doctor?" she asked, he agreed and he and Nancy followed Vishnal.
"Now, our guest it taken care of for the time being, so lets go hammer out these details about how we're going to get those Aura Sphere's back!" she said, getting a nod from the guys and they all headed off to Arthur's study to work out battle plans.
I really have no idea where I was going with this or where it could go, I just got this scene stuck in my head and had to type it out, so there you go.