Haibara's Teenage New Game+.

Natsuki Haibara thought his high school years were a complete failure—until he suddenly wakes up as a freshman again, armed with all he learned in college. Determined to rewrite his school days, he joins the popular crowd, makes friends he never had, and grows closer to his crush. But second chances aren’t as easy as hitting “Restart.” Can Natsuki turn his regrets into a rainbow-colored youth?!