Together with the Demon King's Army - Merging with the Demon King's Soul!? Unlimited magical power and doing whatever I want!

Saotome Riku, who has a weak heart, wakes up from a dream only to be summoned as a Demon King with infinite magical power. This is a story about this timid boy nervously casting massive spells, transforming his castle into a giant dungeon, and attempting to create the strongest demon king army. This is my first time writing. There may be typos, strange Japanese, or delays in serialization, but I would be delighted if you would read it.