After I Picked Up a Sea Monster Sentinel

[The worldbuilding is pretty big. I'll practice some more before writing this.]

Blurb 1:

Lin Yan transmigrates to a desolate planet in the interstellar era.

From the start, all he has is a lame leg, a rickety ship, and a ten-year-old sister suffering from a genetic disease.

To earn enough money for her injections, he sets sail in his shabby little ship. He harvests seaweed when things are quiet and robs robbers when trouble comes. In just three years, he's become a notorious "mad dog" around these parts.

At seventeen, Lin Yan buys a little sea monster covered in scars from a crooked merchant for next to nothing.

He locks the ugly thing on deck to use as a fishing tool. He never expects it to cling to him the moment it sees him, trying to get close and even wrapping its broken tentacles around the boy's ankles several times.

Lin Yan gazes at it fondly.

So it's an idiot.

It actually thinks the person enslaving it is its mommy.

Blurb 2:

Xiu's family has a strange inheritance.

Every few generations, a special Sentinel is born into the family. They awaken the most powerful spirit form in the world, a terrifying sea monster straight out of ancient mythology.

Suppressants have no effect whatsoever on spirit forms like this. Without comfort from a Guide with a high compatibility rating, a special Sentinel will die from a mental breakdown even faster than other Sentinels.

Unfortunately, Xiu is the one chosen.

When he came of age, his mental sea was already on the verge of collapse. He randomly chose a desolate planet to exile himself to, then lost consciousness.

But half a year later, not only was he still alive, he'd also been taken in by a Guide with 100% compatibility?!

[Mini-scene]

Lin Yan carries his bowl over to feed the sea monster he uses as a tool.

The ugly thing presses its enormous head against him, making a series of delighted little whimpers.

(Xiu: Snuggle with me, darling! Could you take these chains off? I'll catch fish for you every day!)

Lin Yan: ?

The cold-faced boy limps back with his bowl and frowns in thought.

"Why does it seem even dumber than it was six months ago?"

(Xiu: qaq)

[Cold-faced, ruthless, possessive little cripple of a Guide bottom X clingy, wronged, big Sentinel top who gets everything in the end]

[Spirit forms: a tsundere little mushroom X a giant sea monster everyone despises]

P.S. There's a size difference. The top has no intelligence at first and acts on instinct, but later regains human form. They'll leave the desolate planet, and the bottom's leg will heal.

Theme: Live well