Cthulhu Gonfalon - Chapter 966: Evil (Part 1)

A teenager named Evan Mason was reincarnated into the magical world of Harry Potter and goes to school at Hogwarts!
With only his knowledge of the future and great talent for magic, he takes the path towards the top of the magic world, only to realize that ever step he took, changed everything!

- Description from Novelupdates

Shuu is a member of the literary club that can’t write. One day, he gets a mysterious message on his phone from a girl called Eina, and from that impulsive contact, they begin to exchange messages. They talk of things like their shared interest in novels and grow close. However, when they try and meet, they discover a shocking truth. Eina lives… not in the present, but five years in the past! How will their love develop, parted by five years of nights…!?

A mysterious natural phenomenon caused the Earth to be plunged into darkness. The world turned into an endless bloody chaos and mankind is on the brink of extinction…

Good and bad luck has followed Zach ever since he was five. Poor guy. His life has been far from the sweet and peaceful paradise one might expect of the youngest son of one of only four dukes in a great Empire.But a little more excitement than expected doesn't stop him from pursuing his dreams of summoning, and perhaps his luck is finally turning once he manages to summon something great.Armed with maids, a scummy gift of luck, and a strong will, Zach sets out to live life as he pleases, even to the annoyance of those around him. First stop: The Academy.