Yin Yang Ferryman, How Did I Become Invincible?

Transmigrating to another world, I became a Yin Yang ferryman.I can go to the underworld, a place unreachable by the living. Above the Yellow Springs, I can transcend the fallen, all within a single thought.Ferrying borrows the Yin path, guiding the living through the underworld, searching for the truth through layers of mist.On the Nine Bends Yellow Springs, ferrying Yin and Yang, and receiving rewards.Malevolent spirits, evil ghosts... Crises abound!It's all for self-preservation."Successfully transcended a living soul, obtained Iron Body!""Sunk into the Yellow Springs, obtained Incense of Merit!"......Wait a minute, I just want to protect myself, how did I accidentally become invincible!?