I Can Buy SSS-Rank Summons with Crypto

[WSA Entry] Earth awakened to mana. Those who awakened could meditate to grow stronger. They could learn spells and, more importantly, summon creatures to aid them in battle! Battle against what? Well, along with mana came dimensional gates, bringing creatures from other worlds. Even Earth's own creatures mutated due to mana, making almost everything dangerous. Kayn didn’t awaken his mana. While some of his friends gained extraordinary abilities, he remained powerless. But he had something they didn’t—money. And a lot of Crypto. His father, Yuri, desperately wanted him to awaken. He searched for ways to make it happen, but everything he learned said it was impossible. Then, Yuri found something even better—a legendary skill book, its effects completely unknown. He handed it to his son. “Hide in this bunker and don’t come out,” Yuri said. “I need to throw them off my trail.” Kayn waited for days inside the bunker until he finally managed to activate the legendary skill book. [Mana awakened] [Analyzing user to determine the most suitable system...] [Crypto System Unlocked] A system where Kayn could complete missions, earn Crypto, and buy anything he needed? It was too good to be true! But before he could test it, disaster struck. A massive ice dragon, bigger than Earth itself, appeared and froze humanity. 99% of the population perished. Some survived, but remained frozen for thousands of years. Kayn was one of them. He woke up 15,000 years later to a world that had regressed to a primitive state, with humankind struggling to survive. Was his father still alive? Is he the only human who remembered how Earth was? "Can I rebuild this world?"