It happens by accident, at first.
He's in a public market in Tokyo, testing the magic, soaking up the energy around him. Everywhere he turns, the ancient is battling against the new. Ancient magic and new beliefs, gods and demons versus technology. It is a curious aspect of Midgard, one that is almost nonexistent in New York where his brother and merry little band resides, but very present in the older countries. Perhaps he'll take over the world from here next. The ancient spirits, jostled by modernity, might be convinced to take his side.
He is so absorbed by his surroundings, confident of his own disguise blending him in, that he almost doesn't notice the impact of someone walking into him and barely notices the stuttered apology.
The concern hits him in the gut like a wave.
That's when he notices her, a small affair of a girl, with an unremarkable, if long, mop of curly hair and the same clothes than practically every other girl her age on the street. The dark, tangling mass of negative energy, of a bad luck curse curling and unfolding in her wake, however, is anything but ordinary.
She has stopped in a shop's doorstep, a few paces away, and is hunched over her inactive phone, her eyes looking up at him worriedly from under her lashes almost a burn on his skin.
Concern. Strong and warm, like he sometime felt from his brother and mother, but never from his father. Never from a stranger. It hits him in waves and curls around him like a forgotten blanket. A forgotten need to be worried over, to be important enough for, uncurls like a traitorous snake in his guts. Stomach churning, he turns heels and walk away.
She follows him from afar, trying not to be seen but failing. She doesn't walk into anyone else, keeps her arms close to her body trying not to touch and infect somebody else with misfortune. She doesn't see it, a black cloud hovering around her and her possessions, or she'd know that it hardly takes on him. He's a mighty God, after all, and her curse is but a strange twist of fate.
She follows him all day, fretting that something will happen to him by her fault. He can see it in her memories, can feel it in her worrying projected his way. It annoys him. How can it not? He's a God, born to be king. He doesn't need nor want being fretted over. It is but sentiment, and sentiment is a defect found in the losing side.
For some reason, he sits in a park, and he doesn't disappear nor change his appearance until is it late enough that she gives up and goes home.
Two weeks later, after being beaten by the Avengers and narrowly escaping being brought back in Asgard for punishment, tedious affair it would be, he's back in the market. He thinks to himself that he's there looking for demons, always present in crowded places. He doesn't intend to bump into a young girl on her way to the tomatoes stand, really.
Several months pass, and he finds himself always going back to that concern, given without prompting (almost) and without familial obligations. A gift, from a stranger. He always sit on the same bench and basks in it, and for the longest time tells himself that he's just mystified by the stupidity of the human race (caring so freely for anyone, for a stranger, really!), and that the misfortune curse is interesting and a spell worth looking into.
After four months, she sits on his bench and asks his name.
He's surprised it took this long to stop lying to himself.