Tyrant of the Deep Sea: I Used Daily Sign-Ins to Become the Sea King

[Apocalypse] [Survival] [Deep Sea] [One Female Lead] [System] [Not a Power Fantasy]

Two hundred years ago, law student Lu Lin climbed into a hibernation pod, hoping to escape a hopeless reality.

When he opened his eyes again, the world had become an endless deep sea.

Humanity huddled inside pressurized underwater cities, paying the terminal class even for the air they breathed.

But he awoke in an abandoned undersea mine.

Fortunately

[Ding! Daily sign-in System activated!]

Day 1 sign-in reward: [Oxygen Concentration Tablets]

Year 30 sign-in reward: [Undersea Floating Base]

While everyone else risked their lives for a single breath of oxygen,

Lu Lin had already built himself a deep-sea empire.

The terminal class?

From today on, I run this sea!

(There are System elements to advance the plot. This isn't mindless wish fulfillment, and it's not a power fantasy.)