Jaku-chara Tomozaki-kun - Volume 2 extra

As a man who had lived for 20 something years and had always considered himself as a straight man, he woke up one day and found himself possessed by a stupid and cute system. Moreover, it was a gong-shou cultivating system?! Let’s see how a shou with raised hackles evolves into a (pseudo)queen shou, incidentally with a story of a hidden loyal dog gong.

- Description from Novelupdates

Vahn was an atypical youth. Due to a rare mutation, his blood had the potential to target and attack ailments within the human body. Touted as a universal cure, people had elevated his status above the norm and given him the classification "Panacea". In the media, he was hailed as a great hero who would usher in a new era or human wellness. However, behind the scenes things weren't so bright. Being a unique individual, Vahn spent his entire youth locked up in a lab with various scientists and research teams using his body and blood to perform endless amounts of experiments. The only solace in his suffering was the various anime and manga made available to him between experiments. He often imagined himself as the protagonist in a world of his own, finally in control of his own destiny. For years he nurtured this desire, until at the age of 14 he died when an organization had tried to kidnap him from the lab...

Traveling through different worlds – this is unscientific!

Get cheats – it’s science!

…

This is a simple story. An ordinary person lives in a different world, farming and raising flowers, studying unscientific science in his free time.

until the end.

- Description from novelbuddy

Mana finally arrived in our world after being delayed for unknown reasons, causing the evolution of everything that had life.

Humans, plants, and monsters all evolved, ushering the planet into a new era in which old laws no longer applied and the only law in the world was the rule of the jungle, where the strong preyed on the weak.

It was a question of whether we, the 'rulers' of the land, would be able to maintain our position and adapt to whatever came after our planet's awakening, and if we did, was that the end?