Paragraphs. Your story is pretty solid, great job on that. What you’re missing is the formatting. You have some long sentences in there that could be split up for example.

Let me show you the difference with some slight changes:

After a long battle with the demon king, the hero emerges victorious. And in glory of coming back alive, the hero and his party comes back to town, but the hero brings something up. "Uuh, where is Luka?" He asks.

"Who?" Maria the cleric questions his strange question. A question square you might say, but it's indeed strange. This name has never been mentioned before, surely something is wrong.

"Luka, my best friend" The hero adds to the name, speaking as it was the truth. But this lonely hero grew alone, on the streets, about to die in a cold winter until... wait... something is quite wrong.

I added a few dots and made paragraphs as you can see. I would recommend making paragraphs whenever a different character comes in and does something.

If there’s no switching at all, keep your paragraphs at five lines long. For sentences, try to keep your max at two commas. These aren’t hard rules. You can do whatever you want, and sometimes they’ll be a bit longer than normal. That’s fine too.

This is just as a guideline, so I hope this helps you out :)