In a world, where monsters take the forms of women who lust after a substance only men can give them, one boy is fated to change everything forever. And to continuously get raped doing so.
The plot starts when Luka, hero of this story, has a dream of the goddess Ilias who commands him to take up arms, become a hero worthy of her and slay the Monster Lord, whose legions of monster girls attack humans everywhere. However, Luka has another ideal: coexistence between human and monster, something Ilias would not approve of.
Luka thus sets out, when suddenly a monster attacks his village. He sets out to defeat it, and barely does so, then wanders in the woods where he meets a young and beautiful Lamia named Alice who mysteriously crash-landed into the ground. Luka checks on her to see if she is okay, but realizing he is too late for his baptism, he hurries back to town, only to come too late.
Returning home, Alice awaits him. After some discussions, in which Alice finds Luka "interesting," they both set out on a world tour - for Luka to fulfill his goals, and for Alice to satiate her gourmet curiosity. However, Alice warns Luka that she is merely observing him and refuses to help him in battle.
The strange couple travels along the continent Ilias, fighting monsters attacking humans, and get to know each other. Luka dreams of peace between humans and monsters, for which Alice continuously calls him stupid and childish. However, Alice begins to acknowledge Luka’s growth and teaches him sword art and techniques, always accompanied by insults and creepy stories. She also later gives him the Angel Halo, an eerie-looking sword that can seal monsters rather than injuring or killing them. However, Luka’s dreams about Ilias urging him to defeat the Monster Lord never back off, either. Alice also learns of Luka’s past and his reasons to become a hero.
They defeat various monsters en route to Iliasburg, but upon their arrival, Granberia, one of the Four Heavenly Knights whose power rivals that of the Monster Lord’s, is attacking; despite Luka’s bravery, it is ultimately Alice’s appearance that causes the insanely powerful monster to retreat, much to Luka’s confusion. Around the area, they also meet a strange Lamia named Amira, defeat the Four Bandits who are terrorizing Iliasberg and receive the Red Orb which Alice hints to have some purpose, solve a problem between a village of humans and harpies, and visit a mysterious town only to be turned back. With everything done on the continent, they decide to make their way to Iliasport and head over to the next continent, Sentora.
At Iliasport, they are told that mysterious tornadoes and rough winds border between the two continents, making it impossible to travel. Fortunately, Amira shows up and informs them of a cave holding a treasure named Poseidon’s Bell, rumored to safeguard any boat from any storm. As he ventures deeper, he fights Nanabi, a right-hand of Tamamo, another one of the Four Heavenly Knights. During their battle, Nanabi puts Luka to sleep, but suddenly Luka unconsciously uses unimaginable powers and begin to obliterate the kitsune, leaving the awakened Luka and Alice in shock.
Just then, Tamamo emerges from deep within the cave, with the bell in her hand. Tamamo willingly hands over the bell (as she was bored and wanted to play with the cave’s traps) while accidentally mentioning Alice to be the current Monster Lord. After she leaves, Luka questions Alice, but is ultimately convinced she is not an enemy, as she claims to have ordered her brethren to attack humans only in self defense, and the two resume their travel.
Aboard the boat to Sentora, they encounter Alma Elma, another of the Four Heavenly Knights who was responsible for the blockade between the continents, and "plays" with Luka before leaving. They then arrive in Sentora’s Natalia Region at Port Natalia, but unfortunately encounter Lazarus, the head of the Ilias Kreuz terrorist organization which was also led by Luka’s father, causing Luka to explain it to Alice.
The duo then set off to San Ilia to meet up with its king, who Luka believes will guide him. Upon arriving, the guards shortly allow Luka an audience with the king, as Ilias came to the king in a dream and informed him that he would meet an unbaptized man named Luka, who informs him to meet with three sages and receive their proof in order to obtain the Goddess Sword, said to make the Monster Lord bow before it. However, Alice calls it blasphemy and shatters the sword, sending the king into a psychological trauma as Alice instead tells Luka to search for the Four Spirits and receive their blessings. They then proceed into the castle’s library, but are once again attacked by Granberia, wanting to see how much Luka has improved since their last battle. At the library, they search for the Four Animists and their Sources book, said to contain information on the Four Spirits, but when Luka opens the book, three book-like monsters pop out and attack; Luka promptly defeats them all, albeit with trouble from the last one due to her resistance to sealing effects but fire, in which Alice accidentally burns the library.
After acquiring the book, Luka learns that Sylph is in Natalia, Gnome in Safina, Undine in Noah, and Salamander in Gold. Since Sylph is the closest, they decide to head there first. Along the way, they receive a request back in Port Natalia about wedding a mermaid and human and cleanse a mansion full of zombies, but encounters a strange scientist-looking person at the manor and the freed ghosts from the manor flock to San Ilia.
The duo finally arrive in the Forest of Spirits, the location of Sylph. After traversing through fairies and elves, who warn Luka of a menacing unknown entity terrorizing the forest, he finally meets Sylph and proves his worth to her, allowing them to bond and giving Luka the power of wind. After meeting up with Alice, the duo then encounter the strange creature: Chimera Dryad. Alice is confused as had never such a monster, but the creature does not hesitate and immediately attacks both of them. They both dodge the attack and Alice responds by unleashing a sea of flames at the creature, but it does not flinch, much to her surprise. Luka convinces her to let him fight alone as it is his duty as a hero, but struggles against the monster until he calls for Sylph’s aid, nullifying the Chimera Dryad’s attacks. After a long and frustrating battle, the beast finally falls. The fairies then come out of hiding, thank Luka, and flock over to San Ilia to prank them.
With everything on Natalia finished, they head over to Safina, a desert region where Gnome lies. They eventually arrive at the Sabasa Castle, whose king requests Luka’s help in rescuing his daughter Sara from the Pyramid. Luka also encounters Amira again who tells him about Gnome, and Luka requests her to gather information on Undine and Salamander. Luka then "rescues" the princess, who was not actually kidnapped but ventured into the Pyramid in order to pass the Dragon Seal Trial held by Sphinx in order to be able to wed Granberia, whom rescued her years back, and Luka also receives the Yellow Orb from Sphinx who only tells him that it and the Red’s purpose is to awaken the Holy Wings with all six orbs in hand.
Nearby the castle is the Witch Hunt Village, whose leader is terrorizing the citizens by using them as experiments. After Luka defeats the leader, he encounters the same strange scientist woman back from the Haunted Manor, but Alice does not sense anything from her and is unable to determine whether she is a monster or human.
Finally heading out to search Gnome in the Safaru Ruins, Luka encounters the earth spirit and proves his worth to her, granting him access to her earth abilities, though Alice warns him that using the earth is much harder than the wind, and that Undine and Salamander are even more challenging in battle. The duo then proceed to the Noah region, concluding Chapter 1 of the story.