A Transmigrate-Into-a-Book Plot Bunny

(I've suddenly been wanting to read a story like this, so I'm leaving this idea here for now. I may change the plot when I have time to flesh it out.)

The gong has spent years building a life and career in a big city far from home. One day, he runs into a former classmate from middle school, the shou, at the lab. Before they can exchange more than a few words, there's an accident.

To the gong's surprise, he doesn't die. Instead, the entire world collapses, and he glimpses the world's true nature in the space between universes.

It turns out the shou is the protagonist of a story about a brilliant but ill-fated hero who overcomes adversity. The stability of the world's timeline depends on his existence, and he absolutely cannot die in a lab accident.

The timeline snaps back to the gong and shou's reunion. The gong takes care of the lab's safety hazards, but becomes fascinated by the life of the shou he glimpsed in that fleeting moment, and gradually gets involved...

Theme: Cherish life and follow safety regulations.