I'm not one to summon beings but as far as my sparse knowledge about it goes, you can't "accidently" call on something(and I mean this in general).
Either you do a ritual to summon something, or nothing happens.
If it was that easy to accidently do it, we would have many stories of people doing so.
And as said previously, those spirits are of Japanese origin so it is highly doubtful they would exist anywhere but in Japan.Maybe they can be found in Japanese communities outside of Japan, but that is just a guess.I don't know how much their link is to the land and how much it is to the people.
I don't get it though, you asked here about this being as if you didn't know, then suddenly you "called upon it" and now knows a lot about it?I'm sorry to say but this sounds not only suspicious(why ask something that you now claim to know about?) but also fake.
Okay this is more about the accident. 1st point to note is there is a proper way of summoning, and there are hundreds of improper ways of summoning. Tbh, most mystics summon their respective deities by accident. For example, the Sikhism founder
Here's the base of summoning. You have to set up a comfy environment for the spirit to pop up and let dude know you want dude

to pop up. Now the proper way in West is charging sigils and chanting enns, in the East is mediation sitting on yantras and probably chanting mantras
And in my case the dark room I am talking about, I was vehemently thinking about a specific Onryu in that room, a specific one on which my eyes fell upon when I was researching, resulting in a mass psychic imprint in that room. That's exactly what happens when you charge a sigil and think about a spirit. And when I switched off the lights and was about get I realised I was not alone and the one Onryu I was reading and researching was there, as the Onryu felt comfortable and could feel the psychic imprints, which were about her. That's what happens while chanting an enn(it's better, unique and directed at the spirit) or any other summoning chant. The spirit hears your call and comes over
Next part, in the spirit plane, there's no Japan, there's no America. Every point is connected to the other. Sure you can ward specific spaces and shield off, but obviously nobody did it for them
The Onryu told me the things I wrote. That's how I 'suddenly know so much'
