Zero no Tsukaima - Volume 18 Chapter 6

Lord of the Mysteries, part two.

In 1368, at the end of July. Bloody scarlet will descend from heaven.

Anyone who could construct a stable Spell Model could become a Wizard — that was the Wizards’ ultimate secret! Having been given a new life as the son of an aristocrat and armed with a super quantum computer from his past life, Spell Models came as easily as breathing to Merlin. With this overwhelmingly huge advantage, would Merlin become the greatest Grand Wizard of all time?

- Description from Novelupdates

In a world where dungeons were an essential part of it, Rein was trying to conquer as many as possible. They were the key to gain powers in the fastest possible way. So, to reach his full potential and to become the strongest, he became a great dungeon conqueror.With his trusty friends and lovers, he was definitely going to reach the peak alongside everyone. Join Rein and see how he went from strong to stronger and then the strongest.__________________1. The harem would not be too large(I'm not sure how many but probably just 4-5 main and few other here and there). All the girls would be getting their time and story.2. The story is starting when the MC is in the middle of his growth stage and not at the very beginning. But his beginning will be mentioned in the story in some form.3. I don't think I need to mention this, but obviously it will not have any NTR, rape or that kind of stuff. It is actually quite a wholesome story focusing mainly on adventure, action and bit of romance and slice of life.

Leguna. An orphan. His life changed dramatically the day the thieves’ guild happened to select him for training and development. He would go on to become lifelong friends with a loyal mercenary, the partner of a beautiful magus who was cold as ice, the savior of a mysterious disfigured dark-elf girl with a talent for the Breath, and the unlikely caregiver for a feisty young maiden. And yet, who would be with him to the very end?