Mrs. and Mr. Smith - Chapter 690 - : Spare No Man or Beast!_1

Protagonist travels between different anime worlds to right wrongs and uncover his reason for being along the way.

An ordinary medical student suddenly got the blessing of the system and could directly see the patient’s health! Since then, treating illnesses and saving lives has become commonplace, and he has also become a legend in the medical field.

- Description from novelbuddy

Crossing to One Piece world, he became Roger’s younger brother.

Unexpectedly, Gol-D-Roger who was in his fifties had a teenage brother. But he was so weak.

Fortunately, at the age of sixteen, he actually found himself with a possession soul system.

He had attached to the master IP man, also to the White Phoenix and to Ge Nie with his strong ability of the Hundred Step Flying Sword.

If you think that he can only Purchase these? Then you’re wrong!

Pain, Itachi, Ichigo Kurosaki, as long as there is money, any soul can be Purchased.

- Description from Novelupdates

An AI calling itself Schema has assimilated earth into its system. As a consequence, everyone gained access to status screens, power-ups, and skills. This AI turned these concepts from fiction to fact. It's easy to become intoxicated with leveling up and becoming stronger. To some, it's too good to be true like living out a dream.

For Daniel, however, it's closer to a nightmare.

He's in a bit of a predicament. Cracks in our dimensional fabric have unleashed terrifying beasts from dark, abyssal places. Schema organizes these cracks into dungeons, giving the native species of the planet a chance to fight back. Daniel finds himself trapped in one of these dungeons. Not long after, he discovers there's only one way out.