Shinjiteita Nakamatachi ni Dungeon Okuchi de Korosarekaketa ga Gift "Mugen Gacha" de Level 9999 no Nakamatachi wo Te ni Irete Moto Party Member to Sekai ni Fukushuu & "Zamaa!" Shimasu!

There are six races in this world: human, beast, dragon, elf, dwarf, and demon. Humans are discriminated against and looked down on as the most inferior race. The "Gathering of Races" was a party with members from each race gathered to dispel such discrimination, but they also had a hidden purpose. They were ordered by the non-human countries to search for the human "Master," and take it to their own country.

Light, a human boy with the gift "Infinite Gacha," was welcomed into the Gathering of Races as he was suspected of being a Master. But in the end, their investigation showed that Light was not a Master. Just as Light was about to be killed by his teammates, he accidentally stepped on a transfer trap and was teleported to the lowest level of the dungeon. In the deepest dungeon, he was attacked by a mythical level 1000 demon. In a desperate situation, Light used "Infinite Gacha" repeatedly. Luckily, he draws the SUR level 9999 card "Mei the Seeker Maid." Mei helped Light repel the demons and saved his life.