Rebirth: Exclusive Love in the End of the World - Chapter 15 - Awakening Ability

Xia Yan passed through to the world of Bleach and became an eleven-year-old boy. He was rescued by Renji and Rukia in the Seireitei, and he was studying at Shin’ō Academy, and he was a student of the same class.
He is a top student of the Shin’ō Academy, and he is vying for strength by various teams. In the end, he has entered the first team of secret mobile maneuvers.
He will use punishment to kill every person who tries to threaten the martyrdom and protect his loved one.

- Description from Novelupdates

When Lu Wu opened his eyes, he found that the world had changed completely.The world before him did not have fancy magic, nor ultimate Dou Qi.What it had were summoners that form contracts with summoned beasts.And coincidentally, he was such a summoner, although not a professional one, and his first summoned beast was a piece of crap.But that was fine, because he also had a golden finger!

Ruins stretched across the landscape in the apocalypse after the nuclear war.

Summoning ceremonies can freely call forth even “those which lurk in the depths beyond the gods”. One boy has top-level abilities even among the cutting-edge summoners who can use those ceremonies. He is Alice (with) Rabbit aka Shiroyama Kyousuke. But this strongest boy summoner has a single fatal weakness. Certain “cursed words” spoken by girls: “Help me.”

When Kyousuke hears those words from Meinokawa Higan, a girl brought to the verge of death, he throws himself into a city where three great summoner forces clash!