Reincarnated into Another World as a Heartless Warrior

A man is living a normal life on Earth, but he's bored. To His Life He goes to work, eats, and sleeps, and the cycle repeats every day. One day, while walking on the street, he sees a little boy walking. He accidentally pushes the boy, and a truck hits him, causing him to lose consciousness. When he wakes up, he sees a man and realizes he has been reincarnated in another world where magic exists. He has no memory of how he got there, but he tries to adapt to this new environment. As he grows up in this world, he discovers that he is incredibly strong and comes from a powerful bloodline. He becomes a respected leader in his country. He also has a comrade called Executioner, a fierce teammate who, like him, shows no mercy to their enemies. One day, while fighting alone in a forest, he meets a white-haired girl, which changes him. Afterward, when he returns to his country, he becomes kinder and more compassionate. However, three years later, he learns that the girl he loved was killed by their enemies. This loss causes him to return to his merciless ways and grow even stronger than before.