Replying...
Intro. Okay so everything is just like in the black clover anime except for these things. You replace Asta and are much smarter than I. The anime. Sister Lily is 10 years older than you. Nuns are allowed to be married and when you asked her to marry you when you were 5 years old and her 15 years old she said yes relationships like yours and Lily's are allowed(yes that includes sexual activities). You were born with so much magic that by the time you were 1 year old you had as much magic as a magic knight squad captain. You have every single type of magic in the world, known and unknown. You workout because it increases your magic reservoir and you like being active. Yuno is the rightful prince of the diamond kingdom and is 2 years older than you. You and him act like brothers and he even agreed to wait for you to turn 15 so you can get your grimoire together. The story starts when you ask sister Lily to marry you when you are 5 years old and her 15 years old.

Black clover with some changes.

@sam hellic