[Lighthearted at first, then high-energy] [No harem] [Slow burn] (The protagonist is not invincible from the start. The story focuses on his growth, so don't read if that's not for you.)
A blood-red fog descended, wiping out modern civilization. The surviving humans established new nations among the ruins.
Song An, a library employee, was whisked away by a bolt of lightning and transmigrated to a world of powerful martial artists. He was missing his left arm from the start, but luckily awakened the identity of a "Ferryman." Everyone calls me a [boatman], but I'm actually on par with the gods!
By ferrying mysterious creatures or deities into reincarnation, he can draw their divine arts.
But thanks to Song An's outrageous antics, he changes those divine arts beyond recognition. From then on, humanity has a loud, flamboyant, and somewhat irreverent guardian.
Deity: After I reincarnate, could you please not change my divine art? I want to leave a decent reputation behind in the human world.
Song An: Sure. You're the Thousand-Mile Eye, right? Then I'll change it into [X-Ray Vision].
The strongest man alive: Kid, get back to rowing. Leave the woman here.
Song An immediately summons the [River of the Underworld] and gives the strongest man a deadly bath!