Well, first, you need to really understand the characters' personalities and motivations in the original story. Then, come up with a unique plot that fits within that framework. Also, make sure your writing style is in line with the tone of the source material.
First, you need to have a deep understanding of the original work's characters and world. Then, come up with an interesting plot that fits within that framework.
The 'How Not to Summon a Demon Lord' manga did finish. It provided a satisfying ending that tied up loose ends for fans. The final chapters brought closure to the characters' adventures.
Overall, the ending of the manga was well-structured. It tied up loose ends and left fans feeling content. The resolution of conflicts and character developments were handled smoothly.
The main character, of course, is very important. Without reading the novel in detail, we can assume that the demon lords themselves are also significant characters as the title implies a connection to them.
One of the main themes is power and its consequences. The protagonist has great power and has to deal with how it affects those around him and the world he's in.