Assassin System Or: How to Stop the Urge of Killing Just to Level Up

[Hello, Master! I am your one and only Assassin System! Please complete my missions for a chance to leave your mortal shell and enter the immortal realm!] Daniel just wanted to live a peaceful life, skimping off from the government's UBI month by month. However, when he went on a whim and climbed a mountain just to see a celestial event, he didn't expect a calamity to strike at him instead! Surviving a meteor impact, Daniel, who thought he was going to die, was instead bounded with an alien system, who constantly want him to assassinate others just to retrieve all the remaining fragments of the system's body! "No! I am just a normal teenager! How do you expect me to suddenly go around killing people for no good reason?!" The system: If Master does not complete your mission within 24 hours, you will die or turn into a vegetable for the rest of your life. Gambatte!