Kyoukai Senjou no Horizon - Volume 8B, Chapter 48: Sweetheart at the Conclusion

Time travelling from the majestic era after the Recuperation of Reiki, he became Kimura Kazuki, a 16-year-old high school student in Japan, one year before the Reiki Recuperation.

Tentatively, he set out to hone himself to the bone, burning candles at both ends to stockpile resources in preparation for the imminent Recuperation of Reiki. His goal was to be many steps ahead of all humanity when the time comes.

However, it seemed like fate had decided to play a cruel trick on him.

One year later, the Recuperation of Reiki… did not happen as expected.

- Description from Novelupdates

This is the story of an orphan, Lu Shu. He is not any regular orphan, but a metahuman experiencing the changes in himself, his country and the world during the dawn of the magical era. Watch as Lu Shu embarks on a journey to hone his peculiar abilities together with his sister, the adorable and charismatic Lu Xiaoyu. Along the way, they’ll encounter supernatural events, obstacles and even the most powerful people in their country. How will Lu Shu make the best of his abilities and oust his never-ending list of rivals and opponents?

During a party one evening in the royal palace, Rachel, the eldest daughter of Duke Ferguson, was reproached by Prince Elliot for sins she didn’t remember committing and their engagement was abandoned. Rachel informed everyone she had not committed the acts they were accusing her of, but she was dragged away out of the party venue and thrown into the palace dungeon.

After breaking up with his girlfriend, he accidentally acquired a genius system and rose from there against the heavens, becoming invincible..

- Description from Novelupdates