I was not expecting it to be good.
It had a very interesting atmosphere to it. I usually don't like linear stories that have no or minimal choices, but I really liked this (oops, only now just noticed choices won't be implemented until later chapters. I'm excited for those!).
I'm not a fan of AI art, I was really iffy about checking this story out because of it. However, after reading, I feel with the setting of the world, you are using it to tell a story that can only best be told if using AI artwork.
I also really liked the music! That's not AI? You did good!
There are a lot of typos though. Grammar and spelling. At least there was in the first part, where the protagonist meets Sam in his world and walks with him. Once they reached the cabin, I stopped noticing it because I was too interested in the atmosphere and setting.
I adore Sam so much. Like, he obviously feels very guilty for luring the protagonist into this strange reality, and is trying to make up for it by cooking and providing for him however way he can. It's explained in dialogue, but even without that dialogue you can tell his actions were driven by loneliness and a desire to keep a new potential friend, and the guilt of bringing him there. I'm also interested in this internal struggle he has, where he wants to leave but can't bring himself to enter these foreign worlds he encounters. I feel most of the inhabitants of this ever changing limbo probably feel the safe way.
I read the comment by Naho. Honestly, it seems to me they didn't pay attention to or read the story at all. The animations were not "distracting" either, at least not for me. Of course, lots of people have things like ADHD or other conditions that make it hard to focus, so I could see how the animations might bother some people. I would not say the animations are "overused", I feel they highlight and attribute to the feel of the setting.
It IS weird though, that you have no idea what an isekai is though LOL.
Isekai is a fantasy subgenre where a character is transported (or reincarnated) into a fantasy world. The protagonist of Interloper walks down a road and enters a different reality. This, by its briefest definition, makes it an isekai.
I will point out, there is more to the genre than that, as many would consider true isekai has more factors to consider that make them such. True isekai heavily involve the protagonist making use of their knowledge of their prior world, and typically the story focuses on the culture and technology of the protagonists new world. Anything less is just the isakai trope being used to jumpstart a story.
Is your story an isekai? Maybe. I would argue it probably is. But only by it's most basic and simple definition, "Character is transported into a different world". There is no need to follow any of the common story formats used by the genre and trope, as your story is too different from the typical isekai to use them.
Just keep doing what you are doing. It is good.
Honestly, I think the story was formatted well, the "suspension of disbelief" you mentioned, I could easily understand what was going on and felt it was done very well. Naho just has no reading comprehension (No offence Naho. But you pretty clearly let your biases cloud your thinking) The only thing I can tell you actually need to work on right now is your grammar. Many sentences read like they are missing words, and there were quite a few spelling mistakes (at least in the first part of the story). And that all would be easily fixed by downloading and using the free version of Grammarly.
I will be waiting for the next chapter.