From Baka-Tsuki:
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.