Harry Potter: Ero World - Chapter 5: Gringotts! Part-3

Aaron, a wildlife biologist, became a military strategist right after a global war between nations began.He never wanted to participate in the war but he had to, because he wanted to continue his studies on endangered species the moment the war was over, but to his surprise, everyone in his unit were killed, including him, and the next thing he knew, Aaron woke up in the body of a young noble having a similar name to his.However, he also noticed he had awoken in a world different from Earth.In this world, demonic beasts ran rampart with only one thought in mind, causing them to feed on anyone they see, be it humans, elves or even magical beasts as well.During his first encounter with a magical beast, Aaron awakened a system which allowed him to bond with magical beasts and to obtain terrifying abilities from these bloodcurdling magical beasts, so he used his experience as a wildlife biologist to help make it easier for him to bond with these beasts.However, Aaron also noticed he could evolve these beasts if their loyalty towards him had reached a certain level, so he vowed in his heart to grow strong enough to protect those he cared about in this world with the hope of living a happy, peaceful life where he'll be able to focus fully on his passion as a wildlife biologist.

An unnamed 34-year-old Japanese NEET is evicted from his home following his parents' death.

Upon some self-introspection, he concludes that his life was ultimately pointless.

Walking down a street he intercepts a speeding truck heading towards a group of teenagers, in an attempt to do something meaningful for once in his life he manages to pull one of them out of harm's way before getting himself in the way of the truck and dying.

Awakening in a baby's body, he realizes he has been reincarnated in a world of sword and sorcery.

He resolves to become successful in his new life, discarding his past identity for his new life as Rudeus Greyrat.

In the City of Crime, one law stands above them all: Only the strongest can live.

I had a supporting role in a modern fantasy.

The loyal dog of a villain with an angel’s name, Cheon Sa-yeon, and an unfortunate supporting character who died on his behalf, Han Yi-gyeol.

In order to escape from Cheon Sa-yeon and survive, he must use the protagonist, Ha Tae-heon.

But Ha Tae-heon, who he thought of as a lifeline, was infinitely indifferent to him. Rather, Cheon Sa-yeon showed interest.

But besides that, something strange happened.

The events that occurred in the original story had advanced, and the gate and monster levels had risen. Even the people were “different” from the original.

The original version I was trying to use was wrong.