I haven't thought of what to write yet, but, I can't be idle, I have to write.
Write mindless novels. Just write whatever you want, forget about the introduction and change it later.
It should work. Write a different one. Why is the protagonist a human? I just stopped being a human and traveled between the world and the world. I just killed monsters, upgraded and changed the map. Fight monsters and upgrade.
This novel and its characters are purely fictitious. Any similarity is purely coincidental and should not be imitated.