Strongest Swordman’s Re:START - Chapter 24: Formalities

Elliot Hawthorne, had transmigrated into the body of a struggling apprentice mage, and now had one simple goal, summon a small, harmless spirit to pass his magic academy’s final exam. But thanks to a mistranslation in an ancient grimoire, he instead summons Azrael, the almighty Demon King.That would’ve been bad enough…. but then the spell accidentally binds them in an unbreakable marriage contract.Now, Elliot is stuck with a possessive, dangerously powerful, and ridiculously affectionate demon husband who:Carries him everywhere because “His cute little summoner’s feet shouldn’t touch the ground.”Summons hellfire just to keep Elliot warm when he complains about the cold.Declares war on any kingdom that dares to call Elliot “single.”Refuses to be unsummoned.“Why would I leave? My husband is here.”Worse, every holy knight, exorcist, and jealous god now wants Elliot dead for “stealing” the most powerful demon in existence.. Stuck with a one-in-a-million system dungeon and a devilish Demon husband, Elliott's life is constantly on the brink of disaster...But when Elliot starts uncovering secrets about the contract, he realizes…Did I really summon him by accident? Or… was Azrael waiting for me all along?One way or another, Elliott’s unlucky life becomes worse. An impending doom threatens the existence of the human and mortal worlds.And as if that wasn’t enough, he’s also stuck with a Demon for a husband.But maybe, just maybe… being bound to a dangerously powerful Demon King isn’t the worst fate after all.

Traveling through the world of pirates, he also became a noble Celestial Dragons.Lakeman just wanted to enjoy a luxurious life.Unexpectedly, as soon as he attended an auction, he met the three Boa sisters who had just been captured, and the binding system was awakened at the same time.If you bind a genius, you can get the other person's daily practice feedback.【You have bound Boa Hancock.】【You have bound Borsalino.】[You have bound One Piece’s deputy, Silvers Rayleigh.】【You have bound Doflamingo.】“Originally, I just wanted to recruit talents from all over the world, but why are there more and more beautiful girls?” Lakeman looked at the group of beauties beside him and fell into deep thought.

He is a young man without a spirit root. It is believed that this denies him the chance at cultivation. However, a mysterious lady imparts a Supreme Demon Classic to him and from then on, he starts his path of cultivation.
He undergoes a total transformation to emerge as the most fearsome and powerful fiendish demon in his era, that even immortals and fiends are fearful of him, and saints are at his beck and call.
Mastering the Supreme Demon Classic is the turning point in his life. He is able to unleash his immense and divine power from within, illuminating the entire universe!

- Description from Novelupdates

What would you say is the most valuable thing in this world?