Maybe a Fake Gintama - Chapter 528: Some Burdens Can Only Be Borne by Adults!

A skilled but unfortunate modern-day assassin was killed in a freak accident. However, he soon found himself summoned to another world by an evil wizard, who had him possess the body of a boy as an experiment. After successfully planning the evil wizard’s downfall, he used the wizard’s body as a springboard to gain influence and power in his new world.

- Description from Novelupdates

Usually when you possess a novel, you start in the city, but I fell into the forest.

Lin Feng was originally in charge of Supermarket supply. One day the supermarket accidentally enters an Apocalypse world. The apocalypse is happening, he has a supermarket in his hand. See how Lin Feng brings a supermarket to survive the Apocalypse.

- Description from Novelupdates

After successfully reaching the Core Formation Stage and forming his Golden Core, Bai Langtian was betrayed by his own Master. His core was ripped from his body, and he was thrown off a mountain cliff into a valley full of demonic beasts.Thankfully, he survived the fall, and met his senior sister, Shangguan Yue Ling.She too had been betrayed by the same Master and pushed into this valley ten years ago. Ever since, she had been surviving alone by eating the corrupted flesh of demonic beasts.Now, Yue Ling revealed to Langtian a new path of cultivation:Demonic Cultivation.To reclaim his strength and take revenge, he must consume the flesh and essence of ten thousand demonic beasts.