High schooler Yuuri Shibuya gets flushed down a toilet after intervening in a bullying incident and lands in Shin Makoku, a world of demons, where he's declared its new Demon King. This manga retells the light novel's story with its own art by Temari Matsumoto, following Yuuri as he navigates palace politics and an unplanned engagement to the fiery swordsman Wolfram von Bielefeld, aided by his loyal retainer Conrad Weller.