"Constantine Madden knew he had magic. His life wasn't one of those ridiculous "I'm-the-chosen-one-and-I-have-been-prophiced-to-save-the-world!" stories, he knew that for sure. (He didn't even think prophecies existed in real-life magic.) He didn't find out he had magic randomly after a crappy life situation. No, he and Jericho, his twin brother, found out when they caught their mom, Eliza Madden, doing magic. Constantine, being the cunning boy he was, approached her and got a confirmation: Yes, magic was real. Yes, he had it."
This is a Magisterium by Holly Black and Cassandra Clare fanfiction. It makes sense if you haven't read it, but will have spoilers for book 5. (Might have an eventual sequel; this might just be Iron year)
Also, Jericho x Declan if you squint...
Transmigrated into DxD World-Kuoh Town, Hibari Kyoya. an average student, spent 18 agonizing years in the world fully aware of the dangers, knowing he is utterly powerless in a world of gods and monsters, Until...
[Ding! Sign-In System loading... 20%... 50%... 80%... 100%.]
Destiny, it seems.. has a cruel sense of humor. A [Sign-In System], long overdue, finally bursts to life within him, offering a chance at survival, a chance at power...
[Ding! Congratulations! You have received the Rainbow-Grade Gift Bag!]
...
He then started completing System's tasks, accumulating even greater rewards.
[Ding! Task completed. Reward: Perfect Rumble-Rumble Fruit (Weakness to water Removed).]
[Ding! Task completed. Congratulations to the host for obtaining the Flying Thunder God Technique!]