Making a Fortune in the Interstellar World by Collecting Scrap

[Main story complete; the first extra chapter is up] Sang Yu opened his eyes and went from being a college freshman to an undocumented resident in the interstellar era. From the start, all he had was a junkyard and three credits and fifty cents in his photonic account. To get registered, he enrolled in school. By day, he acted like a good student at military academy; by night, he hauled a wrench around and took apart mechs. Then he made a name for himself in the placement exam. The whole year was in an uproar: How did that trash-picking last-place student suddenly make it into the top ten?! Thanks to his outstanding results, Sang Yu earned the right to choose his major early. After taking in an abandoned mutant-beast cub, he chose the most notorious major without hesitation so he could care for it: Mutant Beast Command. The Federal Military Academy had an ironclad rule: Mutant Beast Command was a money pit, and F-rank mutant beasts were worthless. When Sang Yu registered a snow leopard cub with a lame leg and a broken tail, everyone mocked him. Then, in practical training... The little snow leopard swiped an S-rank cheetah off its feet and wrapped its tail around a mech's control lever! Everyone was horrified. What the hell, that's an F-rank?! Sang Yu sucked in a breath, then grinned. Hey, did I find a treasure? From then on, Sang Yu became a sensation at the military academy. He also caught Tang Yi's attention. Tang Yi realized there was something strange about this undocumented freshman. He could dig up ancient Earth books in a junkyard, turn the cafeteria's leftovers into mutant-beast nutrition supplements, and even... with his bare hands, take apart and reassemble an explosive aircraft thirty seconds before it blew up... Tang Yi became interested in him. So he took the initiative to approach and make conversation, sending one greeting in the morning, at noon, and at night. Surely that would win Sang Yu over, wouldn't it? But days later, just as Tang Yi was about to send another message, Sang Yu abruptly sent him a payment QR code, with a cold note: Pay five star credits to unlock chat. Tang Yi: ... Theme: Stay on the righteous path