Wow, I actually already wrote an isekai. Actually two. Maybe more if I'm forgetting any. The first one has to do with an angel kid living on a cloud city being talked into jumping off of the said cloud city by a talking balloon in order for it to find its master. It's kind of a reverse isekai since the angel girl falls to earth.
The second one had to do with a writer that had major writer's block (something I don't believe in). It becomes so bad that he can't sleep. And one day, he finally starts to write stuff, and to him, it's the most amazing stuff he's ever seen. But it all turns out that it was a dream. He didn't actually write anything. Because of this, the writer becomes irritable and disbelieving of what is really happening and what isn't. One day a portal appears beside his bed. He looks into that portal to see a battlefield and a group of downtrodden soldiers. After gazing into the contents of the portal he does what any person in his situation would do, he completely ignores it, assuming that this must be a dream. And think about, after everything he's been through, of course he would think that. So what happens next? A roar like a lion mixed with a dragon reverberates from the portal. The writer tosses and turns, and covers his ears by bending his pillow over his head. But the roar grows ever louder. The writer is pretty pissed at this point, and not to mention sleep deprived, so he isn't exactly in his right mind. Assuming everything is a dream, he unfurls the blanket covering him in a dramatic flourish and leaps into the portal, keen to give whatever was making that racket a good beating.
I have a longer version of the first and second stories, but I wrote them so long ago that they're pretty crap. But the ideas were good even if the execution wasn't. I don't really like isekai. It should be a fun idea, but it's more so just a plot device rather than an actual idea for a story.
Oh, I do have another one. It's a reverse isekai where a master mage from a fantasy world gets transported to our world through a battle against another master mage. The other mage basically chucked a black hole at him that simply kept on growing and growing. The isekaid mage knew that he had to stop it or else his whole world could have been destroyed. So he jumped into it and deactivated it. The only hitch in his plan was that the black hole transported him to our earth.
Man, I should really go back to some of my earlier stores. Some great ideas there.
aaah wow poor him. That's a really interesting idea though. If this ended up being a tragic story about the MC doing his best to return home to his wife( and kids?), I would be interested in reading it.