He Just Became the Demon Emperor and Was Summoned by the School Beauty to Become a Beast?

I, Xu Changsheng, am a one-horned sky-swallowing beast, and I am also the only being in the Shifang Continent that has successfully proven to be the Demon Emperor in ten thousand years. Just today, I am going to break the void and enter the river of time, because I have another identity, the Blue Star Traveler. This time I must go home. "I have attained enlightenment as the Great Emperor, and I will rule for eternity." "Blue Star, I'm determined. Even if you are the will of the world, you can't stop me. That's what I said." Once the void was shattered, when I opened my eyes again, there was a cold and ascetic girl standing next to me. I seemed to hear her say: "I, Ye Qingli, seem to be wasted in this life." … I, Ye Qingli, was one of the top ten beast-controlling emperors in Blue Star in my previous life. I suddenly became famous as the Ice Phoenix Emperor with a B-level beast-controlling one. In the final battle in the Valley of the Gods, because the beast control level was only B, they were defeated by the extraterrestrial demons, and they were both killed by self-destruction. However, God had mercy on me, and when I opened my eyes again, I was reborn as a freshman in high school. In this life, I vow to awaken the strongest beast. After three years of hard work, I have cultivated up to 300 points of mental power. In this world where 200 points of mental power can reliably summon S-level beasts, I dare not imagine what kind of monsters I will summon? However, on the day of the summoning ceremony, a "black dog" fell from the sky. Ye Qingli: My family, the rebirth hack has been banned. I spent 300 points of mental power to summon a "pet dog"? However, I gradually discovered that his origin seemed unusual. I vaguely heard him say: "I once shattered the void, and also tore apart the long river of time..."