College student Hiroki Sakurai is pulled from his ordinary life and summoned to the kingdom of Biznad alongside two classmates, Ruri Takanashi and Ren Watanabe. The king orders the three to defeat the monsters that threaten the realm and grants each of them a job class. Hiroki receives the Priest class, a role that grants him exceptionally high natural recovery power. Reasoning from his experience as a gamer that a healer who never takes damage is the most effective support, he invests every single one of his stat points into evasion, aiming to become what he calls a perfect evasion healer.

The king and the court do not understand this decision. They see only a healer who cannot fight and has no defensive stats, and they quickly label him useless. Hiroki is imprisoned briefly and then cast out of the castle, forced to make his way alone. With no other options, he registers as an adventurer in the nearby town. Initially shunned by other parties for his unconventional build, he eventually finds a group willing to take him in: the leader Froitz, the mage Tina, and the frontline fighter Dia. Through them, he learns how magic and stamina work in this world and begins to refine his unusual fighting style.

During his travels, Hiroki encounters Lusha Prime, an elf archer who has been abandoned by her own party. She poured all her stat points into attack power and none into accuracy, meaning her arrows almost never hit their target and pose a danger to her own allies. Seeing a reflection of his own rejection, Hiroki realizes that their weaknesses are complementary. Her attacks never land on enemies but cannot hit him either, since he dodges everything. In return, he can heal and support her without fear of friendly fire. The two form a partnership, and their synergy proves remarkably effective in battle.

Hiroki learns that Ren, one of the classmates summoned with him, has been placed under a powerful curse as part of the king's schemes. To save him, Hiroki and Lusha embark on a journey to find rare ingredients for a curse-breaking potion. They travel through dangerous dungeons, including an underwater labyrinth and a deadly forest, and eventually cross into the demon continent. Along the way, they acquire powerful equipment, level up, and meet allies such as the ancient alchemist Pino.

After successfully curing Ren, the group learns that the key to lifting Ren's curse and finding a way back to Japan may lie with the demon king. They travel to the demon king's castle, where they meet Tito, a demon lord candidate who is preparing for the tournament that will decide the true demon king. Tito tests Hiroki repeatedly through games, poisoned feasts, and dangerous magic, but Hiroki responds without hostility and earns the demon's trust. In return, Tito gives Hiroki hints about how to return home.

With Tito's permission, Hiroki explores a secret dungeon beneath the castle and discovers more clues about his original world. As Tito prepares to compete in the demon king succession tournament, Hiroki volunteers to act as his supporter, using his evasion abilities and healing to aid Tito's bid for the throne. The story follows Hiroki's journey as an unconventional healer who redefines what his class can achieve, while he and his companions search for a way to break the kingdom's hold over them and find a path back to their own world.