In a world of adventure, heroes have strong allies and Rud is supposed to be the strongest defense tank.
Rud fulfills his role as usual, absorbing damage and protecting his teammates while letting them attack, however, this time his defense seems to break down.
Back in the guild, he fantasizes longing for his sister, who has a rare illness, Nin, one of his team members, wakes him up from his dream.
The team leader arrives with two new members. Each party can hold only six members, and he informs Rud that he is no longer needed.
Rud simply accepts his fate and leaves, promising Nin to meet her in his hometown, Avancia.
Later, Rud decides to go home to his sister and finds a few kids taking up a job to escort a client and requests to join them. They recognize him as part of the Hero’s party and accept him.
As they make their way, the path gets incredibly dangerous, and Rud steps out of the wagon to inspect the surroundings. At the distance, he spots an injured girl, she is barely clothed and Rud is able to see a magic stone embedded in her chest.
Before he can say anything, a huge forest snake appears and attacks the group. Rud provokes it to draw its attention and blocks the poison spray with his shield.
Finally, with good command, Rud leads the young adventurers to defeat the creature, and together, they claim victory.
Rud approaches the little girl and offers her to travel along with him. He understands that she is a homunculus, created by someone, but she seems different from others.
The next morning, Rud decide to part ways with the adventurers, who plead with him to join their group, but he tells them he has to find the Secret Treasure to cure his sister.
The little girl comes along, and Rud ends up naming her Luna. At night, Rud prepares to sleep, but Luna spots three wolves ready to attack.
Luna uses a knife to kill them, and Rud realizes she is an illegal homunculus and is hence meant to be disposed of.
Rud also learns that she has an incredibly rare identifying skill. And asks Luna to help him identify the rest of his skills. Now, he will be able to improve and become stronger.
(最強タンクの迷宮攻略 ~体力9999のレアスキル持ちタンク, 勇者パーティーを追放される~)