In Danmachi with Plasmids (New Version)

A man who once lost his family in a tragic accident spent the rest of his life consumed by overwork, desperate to prove his worth to a world that never cared. His struggle ended in exhaustion and an early grave. But death was not the end. Given a second chance in a parallel world, he devoted decades to research, seeking the key to crossing into other realms. Yet even with knowledge, power, and fame, his life ended as before—isolated, unsatisfied, and weary of endless labor. Now, fate offers him one final path. In a world ruled by magic and gods, and armed with a power unlike any other, will he at last reach the dreams he’s chased across lifetimes? Or will his differences cast him out once again? — Description from novelcodex.org