MTL - Rescuing the Supporting Character - Chapter 127 immortal? monster? eighteen

As a promise, he went out into the world as an assassin. 3 years later, after becoming the Supreme Assassin, he gave up on everything he had and returned to the ranks of ordinary people. But one day, Kismet, a mystical game created by the National Research and Development had appeared.

Enigmatic hands, spectral frame, and one cunning strike just like the swing of the Grim Reaper. The Supreme Assassin takes on the mystical world, and how his legendary tales sets off, progressively ascending the altar to becoming the best.

- Description from Novelupdates

They love gold, and they love silver. Even more so, they love gems that dazzle, like stars across the skies.
Firearms, jewelleries, and precious metals; A collector’s world will not be complete without antiques.
Storage auctions, old goods trade, re-estate sales and gold-digging. But the truth is, if one wants to make money, then the supreme way is through searching for the legendary treasures.
Holding the fort, there’s an ocelot, a wolf, and an Andes condor. At the side, there’s a loyal hound, an irascible ape, and an African honey badger. Who said that you can only rely on humans when treasure hunting?!

- Description from Novelupdates

Arthur got randomly transported to another world. Some people would find that terrifying, but not for him, who was tired of his old life; it was an opportunity.

And, after having bad luck all his life, the tide changed.

It was a world of magic where wizards fought side-by-side with their familiars. Arthur got summoned to be one of these so-called familiars.

He was furious. The thought of becoming a pet was not something he liked. Well, that changed when he saw who his master was.

A hot-woman. And, to make everything better, Arthur was inside the Frostpeak Magic Academy, which only had women students.

“This is heaven. All familiars are beasts, but I'm different. I'm a good-looking man inside a place filled with hot girls.”

When he thought his luck could not get better, he unlocked a system that helped him with everything. Of course, he used the system for a greater good, like getting girls.