Zhi You Wo Neng Yong Zhao Huan Shu

Zayn Ze travels to a parallel universe where people grow stronger by fighting monsters in the Demon Realm to prevent them from invading the Summer Nation, the real world where he currently resides. To protect his sister Nina, Zayn enters the Demon Realm under the alias "Loki." However, he unexpectedly awakens with the rare and overpowered SSS-level Summoning Skill! This ability allows him to summon and control every monster he defeats. As his Summoning Skill grows stronger, it becomes a trump card that can tip the balance in this dangerous world!

(Source: WebComics)