Treated as incompetent → In fact, the strongest adventurer! Magic value is 1, which is as close to 0 as possible, and the lowest adventurer rank, "F". Nine spends his days as a vanguard (attacker) in a party that has found him, but he and his beloved cat, Enu, are forced to do all the chores. However, one day, the leader sells off the black sword, a memento of Nine's father, without permission, and even uses violence against his precious Enu and Nine's patience reaches its limit! "I'm quitting now!'' Nine, determined to leave the party and start a new life, is suddenly confronted by an S-rank adventurer "Dahlia of Flash''. And then he is scouted by the strongest party on the continent, "Red Hawk"...?

The Jester ―― More commonly known as the ‘Playboy’ Dylan, was fired from the party of the Heroes. The self-centred Heroes didn’t understand Dylan’s importance to the group. They were just a group of one-man teams. Not interested in cooperation at all. Any failures are blamed on the jester. Dylan, who was disgusted with such companions and was sick of playing as their comedic foil, happily accepted being kicked out. The Heroes didn’t know. After saving them many times over with his magic tricks, the level 99 jester can change his job title to that of a ‘Great Sage’. “Life, how about a rewrite?” He’s done being the clown. From here on out, he’s going to take the leading role.

Fifty years ago, countless Kaiki seeds flew in from space. The world established defensive lines to counter the monstrous Kaiki, and humanity barely managed to survive. Time passed, and now, Shinohami Ai, having completed two years of basic training with the United Human Forces, was heading to the front lines with her comrades when they were attacked by Kaiki. In this attack, her entire unit was annihilated. Abandoned by her allies and with no rescue team in sight, she was left alone at the far end of the front line, in enemy territory. There, she discovered someone on the verge of death from a Kaiki attack and risked her own life to save them. However, the one she saved, at the cost of suffering a fatal injury herself, was Nosferatu, the king of the monstrous Kaiki. To survive, Nosferatu merged with Ai's body. Thus, a new soldier was born with the power of immortality, destined to become a hero - reviving stronger each time they die.

The story follows Lana, who lives in a country where every person is granted a skill by the queen on their 15th birthday. Lana is given the skill "Breathing" (Kokyū), a skill he has never heard of, but he has always dreamed of diving into a dungeon as an adventurer. The skill is basically a joke and initially seems to only do what it sounds like: allow Lana to breathe. Initially he plans to give up his dream, but then decides to challenge the dungeon anyway in order to rescue his sister, who is currently asleep under a witch's curse. Lana has one year to reach the bottom level of the dungeon where the cure lies. Lana is determined to reach the bottom even without the benefit of a skill, but what he doesn't know is that he actually was gifted the strongest skill "Kami Kokyū" (God Breathing). ---