Dungeon Seeker

One day, Junpei Takeda, a high school student, was summoned to another world by a "god" on a whim, along with a delinquent, Shota Kido, and Junpei's childhood friend, Noriko Tatsumiya. They thought they were summoned as heroes, but for some reason, Junpei's status was worse than that of a villager. On top of that, he was pushed into a monstrous labyrinth with zero survival rate by those traitors. Junpei was almost ready to die in this desperate situation, but he came up with a clever plan to recover from the situation. The weakest dungeon seeker has found a way to explore the labyrinth and begun to take revenge on the traitors!

(Source: Alpha Manga)