Shadow's Oath - Chapter 50

Following a brutal and tortured death, a former assassin, known only by his codename Kuro, is given the opportunity to reincarnate in another world, a world with magic and monsters. Armed with an unrivaled healing factor and an inhumane pain threshold, Kuro opts to go for a reckless direct approach in this world instead of a stealthy and cautious one, and as a result, slowly gains attention bit by bit.

Having previously been a loner in his old life, he interacts and befriends people for the first time in his existence, however, his blunt nature also sees him making just as many enemies, both big and small. By combining his old assassin skills with the magic powers of this world, along with his high resistance to pain and rapid regeneration, he doesn't take long to establish himself as a formidable force in this world.

Initially, Kuro only faces minor threats, like weaker monsters and bandits. But before too long, the threats slowly but surely become more and more severe…from Zombies to a bloodthirsty empire to Vampires and Demons, and even divine beings…however, as the enemies he faces grow stronger, so does Kuro, gaining rare powers that have never or rarely ever been seen in this world…

“Hmph, my dumb big sister is in danger!” A mischievous grin spread across his face. “Hehehehe... this gives me the perfect excuse to finally use this treasure I’ve acquired but never bothered with!” He rummaged through his belongings, carefully selecting various items. “A bit of this... and this... and a dash of this.” Boom! The explosion of energy sent a ripple through the air as he laughed maniacally. “Hahaha! It’s done! Now, all I need is a compatible host for it.” Years later... “Did I overdo it?” he wondered in awe, watching as his creation wreaked havoc, conquering world after world with ease, as though stealing candies from children.

An old MMORPG called Live Dungeon. Before the service was terminated, Kyotani Tsutomu made full use of 5 notebook PCs to clear the game and was invited to a different world. And then, Tsutomu was speechless when he saw a live relay of a dungeon capture in the different world. They bulldozed through without any thought of strategy. The misfortune of getting the healer position. Tsutomu reinstated the White Mage that had always been his favorite in games and aimed to conquer the dungeon to find the key to his escape from the different world.

My reunion with her took place in the worst possible way.