Toaru Majutsu no Index SS - Volume 2, Chapter 7: Someone Behind the Scenes is Unprepared and has to Clean Up. The Second Friday of May.

Violet skies, a world undergoing massive changes, a deficient moon, interlinking voids…
When the world experienced a cataclysmic event,the majority of living things ceased to exist. Although humanity survived by hiding in the last safe zones, humans had to face mutated dire beasts and colossal source beasts that could break through the space barrier and enter the earth at any second.
Luo Yunyang, a young man who grew up in those calamitous times, obtained an attribute regulator and set out to walk the path of supremacy!

- Description from novelupdates

Reach the peak of immortal cultivation and become able to run amok without fear! Use the power of martial arts to rule the world and defeat heroes! The weather changes at the whim and wave of a palm. He who cultivates both immortal techniques and martial arts, who could possibly defeat him! Xiao Chen is a shut-in who purchased a ‘Compendium of Cultivation’. Soon after, he crossed over into the Tianwu World, a world ruled by martial arts. He then refined pills, drew talismans, practiced formations, crafted weapons and cultivated the Azure Dragon Martial Soul that had not been seen for thousands of years. This is a story that tells of an exciting and magnificent legend!

Kuramoto Daisuke, a freshman in High School was suddenly exposed to someone vanishing in front of him. Turns out he was admitted to a Special Class full of Isekai Heroes that were regularly summoned to Otherworlds since the start of their Middle School. He was told that he was to become their Support to prevent each of the Heroes' fate of dying in the world they were summoned into. Though mediocre, he realized that his ability has a great potential but it needs a lot of hard work on his part.

Unconvinced of being just the Support Character, he vowed to excavate his mediocre ability, all the while supporting the Heroes using it.

And maybe more.