I'm Just a Student With the World's Strongest Weapon, That's All

Luo Ze, a young man who had only recently started university, returned to his high school days for reasons unknown. He also acquired alien technology from a Level 20 civilization. How will he use it? What kind of high school life will he experience this time? [The protagonist's watch is the one from the Ben 10 reboot, though the original series will also appear.] An anime crossover slice-of-life story with a slow pace and a bit of everything. To ordinary people, the protagonist's X-Man will seem to make decisions incredibly quickly. He uses his beat-up little watch as his ultimate weapon, though he rarely brings it out. Think of it as an ultimate evolution of the golden finger that he hardly ever uses. It will also fuse with alien heroes.