How to Turn Down Your Nemesis's Invitation to Romance

My work situation has changed recently, so I can't start posting this story according to the original plan. Mainly, I can't guarantee regular updates if I start posting now. I'm going to build up a backlog and wait until things in real life are more stable before I begin. [Obsessive, inescapable, perverted Demon King seme x short-tempered, stubborn, soft-hearted Hero uke] The Hero Ian and the Demon King Mesues are sworn enemies. The most infuriating thing is that Mesues is immortal. No matter how many times Ian kills him, he comes back after a while, without caring about the time or place. When Mesues barged into the bath while Ian was washing, Ian finally snapped and raised his middle finger. "Mesues, I'll find a way to get rid of you!" Then Mesues dragged him into the abyss of endless nightmares. Before falling unconscious, Ian heard Mesues say to him in a voice both pitying and delighted, "Sleep, my dear Ian. I'll make you understand that you and I are inseparable, sworn enemies like light and darkness." "I am the fate you cannot escape." [Dream One] Ian is the Hero foretold to destroy the Demon King, but just as he sets out on his quest, he falls prey to the lure of money. Luckily, he meets a half-elf brother who's loaded and invites him to join his adventuring party. The brother is a wonderful teammate, an amazing support, and great at taking care of the home. Since he joined, Ian has been living comfortably and no longer has to sleep on a mat under the open sky. Until he discovers that his brother is the Demon King. The brother sadly explains that he's been cursed. The Demon King is a second personality brought out by the curse, and he has no memories of being the Demon King. Ian sympathetically pats his brother on the shoulder and asks how to break the curse. The brother: A true love's kiss. Ian: ? The brother: Dear Ian, you'll help me, won't you? [Dream Two] Ian is a royal knight. He will disguise himself as a princess, dressed as a woman, marry the Demon King who intends to invade the continent, and kill him to save the world. On their wedding night, the attempt fails; on their one-month anniversary, it fails; on their hundred-day anniversary, it fails... Not only does he fail every time, he also discovers tiny horns, the mark of an incubus, growing on his head... That damn Demon King secretly made him drink a potion that turns him into an incubus! [Dream Three] Ian remembers his real life, but doesn't know he's in a dream world. He thinks he's gone back to the past. So he rescues Mesues before he becomes the Holy Son of the Church, and before he turns evil and becomes the Demon King. Looking at his ten-year-old nemesis, Ian begins the arduous life of raising a child. Actually, it isn't all that hard, since his young nemesis is even better at supporting a family than he is. But Ian is terribly troubled by the mischievous schemes the little brat keeps coming up with. Until he discovers that his nemesis is reborn too... · Mesues personally created three dreams for Ian. To make them feel real, he even erased his own memories in the dream worlds. He intends to use the dream worlds to force Ian to admit his feelings for him, then make Ian accept and submit to the real him. But the three dreams slowly turn into Ian's judgment of him... Mesues thought love meant taming someone. He just never expected to be the one who was tamed in the end. Ian is also the fate he cannot escape. Tips: Enemies-to-lovers, 1v1, happy ending, my take on Western fantasy, lots of original worldbuilding Theme: Good and evil are two sides of the same coin.