At first, it's likely to be very tense. Draco would be suspicious of Harry's motives for protecting him. He might think it's some sort of trick. But as time goes on, they start to understand each other better. Harry realizes that Draco isn't all bad and Draco sees that Harry is genuinely trying to help. This could lead to a grudging respect between them. Eventually, they might even become friends, or at least allies.
The relationship development is a slow process. Initially, there's a lot of hostility. But as Harry protects Draco from real and immediate dangers, like a hex from a rogue wizard or getting caught in a dangerous magical experiment gone wrong, Draco begins to see Harry in a different light. Harry also starts to see Draco as more than just a bully. They might start having conversations that they never thought they would have. For example, they could discuss their dreams for the future of the wizarding world. This sharing of ideas and experiences gradually builds a connection between them that transforms from animosity to something more positive, whether it's a form of friendship or a unique partnership.