Bound to my Enemy - Chapter 87.

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…!?

Let’s fight! Go! Who am I afraid of with a chip that turns into a brain cell? ! Get promoted and get rich! The nest treasures are all mine!

- Description from novelbuddy

The former mercenary assassin Chen Tianlong has been asked to be the bodyguard and private doctor of Lin Wushuang, a pretty lady who is still a student. Their stories in the campus begin.“What's wrong, Tianlong?”“Your daughter is not sick, it's just that her Yin Qi is too heavy. The treatment for her is quite simple, find a man with abundant Yang Qi... and let him hold her while sleeping.”“This concerns Wushuang's life and death, and I definitely trust Tianlong, so let him try.”

The world is terrorized by the powerful Black Witch who has been sealed in the moon. Every ten years, the night of Hexennacht arrives and a chosen witch must battle the Black Witch in hopes of finally defeating her.

As the current decade’s Hexennacht approaches, a mysterious girl named Kagami Kagami arrives and meets Horinouchi Mitsuru, the daughter of the previous Hexennacht representative.

It takes place between Kyoukai Senjou no Horizon and the City Series, two other series by the author.