Complex sentence: One day, a mysterious man named Ryō Yoake offers him a job opportunity, but first he needs to becomes a tester for ReLife: a scientific experiment to rejuvenate him by 10 years and send him back to high school as a student.
Split into simpler sentences: One day, a mysterious man named Ryō Yoake offers him a job opportunity. But first, he needs to becomes a tester of ReLife's experiment-a scientific experiment to rejuvenate him 10 years and send him back to high school as a student.