The Legend of the Demon Martial Emperor: An Isekai Cultivation Adventure - The Legend of the Demon Martial Emperor, #2

In the Yi family of Hongcheng city, Yi An was an insignificant member, but after his father's disappearance, Yi An and his mother suffered bullying. Until three years ago, when an accident occurred, the real Yi An ceased to exist. The current Yi An is actually a devil cultivator who has crossed over from another world. After three years of tempering, he rose from the ruins. With the body of a devil cultivator, he broke free from his shackles and looked down upon all others...
A young devil cultivator, reborn into this other world. Here, his brilliance soars again. No devil is too formidable, no devil too fearsome...   ---   During the battle with several opponents, Yi An had only merged a sliver of the energy from the Monster Beast Core and used his Black Water True Qi to suppress the rest of the energy within his body. Now that the trouble had been dealt with, Yi An found a place to thoroughly refine the Monster Beast Core. If one fails to completely refine the energy of a Monster Beast Core and allows it to remain within the body for too long, the person will eventually be affected by the beast's primal force, leading to erosion by the beast's energy, loss of sanity, and transformation into a humanoid monster beast.