Type-Moon: Humans, I Love You So Much

In ancient Britain, the usurping dragon Vortigern colludes with the Saxons to seize the throne, forcing Uther to flee with Vortigern and grow up in distant Brittany. At the age of 16, they meet Merlin, the flower magician. Under Merlin's guidance, the young Red Dragon and White Dragon find the sleeping Gray Dragon.

"The three young dragons will raise the banner of resistance, overthrow Vortigern's rule, kill the usurper, drive away the Saxons who invaded their land, and regain control of this land!" The three dragons take up the weapons Merlin gives them and set out on the road to becoming heroes, gathering an army and starting a war.

But no one would ever imagine that those noble heroes would also become foolish and tyrannical kings... "My dear children, I love you so deeply. In order to protect you from being hurt again, let us go to the beautiful Avalon along with this world!"

The male lead's main class is Lancer, and he becomes a Grand Servant in the middle-to-late period of Britain. The early part may be rather dull, so please bear with it.