The Gryffindor characters from Harry Potter like Harry himself would probably be very bold and upfront when interacting with the characters in Highschool DxD. They might immediately jump into helping with any dangerous situations. Hermione, with her vast knowledge, could start analyzing the different powers and hierarchies in the DxD world. And Ron might be a bit more cautious but still curious.
If we consider the characters from Highschool DxD, the devils might be initially wary of the wizards from Harry Potter. They could see their magic as a threat to their power structure. However, the more friendly characters like Issei might be excited to learn about this new form of magic and try to befriend the wizards. The angels in Highschool DxD might view the wizards as something in between good and evil, depending on how they use their magic. The wizards, on the other hand, would be very confused by the different species and power dynamics in the DxD world at first. But as time goes on, they could start to form alliances based on mutual interests, like fighting against a common evil force that threatens both worlds.
In a crossover fanfiction, Harry Potter characters would bring their own values and ethics to the interactions. For instance, they have a strict code against using dark magic. When they see some of the more morally ambiguous actions in Highschool DxD, like the devils' use of their powers for personal gain in some cases, they might try to persuade the DxD characters to follow a more 'ethical' path. The Highschool DxD characters would find the wizards' magic fascinating. Issei, being a pervert in his own right, might make some inappropriate comments at first about the female wizards, which would surely lead to some comical or tense situations. But overall, through different adventures and shared goals, they would gradually understand and respect each other's ways of life.
Chapter 224, "Cold Resistance Level Classification, Gains and Persuasion", is the clearest early answer because Long Mountain finally turns buildup into a real advancement. A useful checkpoint is the way the scene starts with If Long Mountain only refused other camps to merge, it wouldn't be... and follows through with Such domineering actions, this Long Mountain....
Chapter 257, "Straightening the Road and the Beast Meat Problem (Part 3)", is the clearest early answer because it turns Qiu Peng's situation into a concrete plot event. A useful checkpoint is the way the scene starts with The young man smiled helplessly upon hearing this and said, "The... and follows through with The camp already has such a large population, and with 40,000 more,....
Chapter 229, "The Dust Settles, Beehive in Hand (Part 2)", is the clearest early answer because it turns Xia Chuan's situation into a concrete plot event. The setup is Hou Ming, stop it right now!" Hou Ming was slaughtering the Beehive's..., but the pressure keeps building through Upon hearing Chen Yingba's furious shout from behind, he immediately....
Chapter 285, "Two Clans in Turmoil—What Does White Dew Gu Want to Guard? (Part 3)", is the clearest early answer because it turns Xia Chuan's situation into a concrete plot event. The chapter turns that into something concrete by moving from By the end of April, after the situation in Longyou settled down, the... to So many Cold Beasts in Redwood Ridge have actually all rushed into.... What makes it stick is that the chapter closes with "Alright, let's settle this like so.
Chapter 278, "Thousand-eyed Demon Sheep, Terrifying Power, Spiritual Medicine 3", is the clearest early answer because the rescue effort creates visible on-page results. The chapter gives readers a real answer by opening on The biggest problem with this unexpected disaster was obviously that... and ending on Xia Hong led the group to the top of the fallen tree and looked in....
Chapter 236, "White Dew Gu, Despairing Yuwen Dao, Yang Lu", is the clearest early answer because it turns Wu Ming's situation into a concrete plot event. The setup is After all, Yang Lu is a giant camp, with a population of just over..., but the pressure keeps building through Six days ago, the Wushuang and Hanqiong families joined forces to....
Chapter 271, "Eliminated, Breakthrough Wave, Green Lotus Grass", is the clearest early answer because Xiang Ping finally turns buildup into a real advancement. The setup is Arena number three, tenth match for Meng Ning, starting now!" "Arena..., but the pressure keeps building through The main road of the Inner City was bustling with noise..
Chapter 290, "Bountiful Harvest—Store Land or Store People", is the clearest early answer because it turns Xia Hong's situation into a concrete plot event. A useful checkpoint is the way the scene starts with Entering the Wushuang Realm, realizing that Long Mountain could no... and follows through with Xia Chuan also nodded, continuing: "Excluding Wushuang, Xia City,....
Chapter 205, "Director Emerges from Seclusion, Treasure Offering Opportunity (2)", is the clearest early answer because Luo Yuan gets a payoff that changes the stakes. The chapter gives readers a real answer by opening on There's more people coming, fifteen hundred, no, nearly two... and ending on Then, an iron arrow suddenly pierced through the rooftop..
Chapter 276, "Integration of Soldiers and Hunters, Military System, and Roll Call Hunt (Part 3)", is the clearest early answer because it turns Xia Hong's situation into a concrete plot event. The chapter turns that into something concrete by moving from Chen Yingyuan and Peng Bo arrived late, clearly not hopeful, out of... to Once the structure of the Cloud Jiao Army is complete, set off to....