Continuity is the Father of Magical Power...?
After diligently training his magic every day, Leons found out that his specialty magic, Creation Magic, is trash! However, with his unbelievable amount of mana and amazingly good luck, Leons is able to turn that useless magic into a very convenient magic to create various things, like a super masochist magic sword that can speak for example! Moreover, he also got closer to Princess Sheria and the grand daughter of the Holy Maiden, Riana, after he presented his creation to them!
The main character, Leo Forster, was reincarnated from another world, as was his grandfather, the former hero, Kento Forster.
Kento begins training Leo in melee combat, and as part of his training, later takes him to a dungeon, along with Leo's two female companions.
They fight their way to the boss of the dungeon, a demonic-looking creature, which deals Kento a mortal wound. This enrages Leo, and he promptly cleaves the monster in twain with his sword.