MTL - I Am Invincible From the End of the World - Chapter 960 chain reaction

The protagonist, Punk, is a cautious, cold-blooded, and ruthless Mage.

His goal is always his top priority, over feelings or morality. When unnecessary, he doesn’t like to act like pigs to eat tigers; there are almost no life and death struggles, sometimes risky but steady progress. No strong enemy everywhere, Instead, Punk is always a strong enemy of others.

And he has a very keen interest in the secrets and teachings of the Netheril civilization.

In a world where summoners wield the power to call forth vampires, elves, angels, demons, and all humanoid creatures from across the realms, Nathan found himself unable to summon beings except from beasts. However, those beasts are not ordinary beasts. They are divine beings who once stood at the same level, if not higher, than the legendary creatures the world ever knew. Casting his gaze to the left, Nathan sees numerous summoners accompanied by the likes of demon kings, archangels, vampire progenitors, and other legendary beings. Turning to the right, a massive army of alien symbiotes is waiting to attack. There was no fear in his eyes, because standing on his left is a majestic wolf who managed to kill a god, the legendary eight-headed serpent coils on his right, above him is the bird who is glowing like the sun, and behind him is a dragon that once gnawed the roots of the world tree. “Let the war begin.”

Entering Tokyo in the bubble era, in this strange era, the only familiar ones are Matsuda Seiko, Nakamori Akina, Kudo Shizuka…

- Description from novelbuddy

The empire has turned into the land of the undead due to a spell gone wrong. God summoned heroes from countless worlds to purify the empire and plant new hope. Lee Shin Woo, an ordinary earthling, was also summoned. As an undead, that is.