Natsuki Haibara

Once a college senior drifting through a lonely and colorless youth, he unexpectedly found himself sent back to the very first day of high school. Armed with an adult mindset and deep regret over his past, he launched the so-called 'Rainbow Youth Plan,' using his accumulated life experience to actively work his way into the social core, striving to make up for lost opportunities, forge meaningful bonds, and pursue a first love he had once let slip away—embarking on a second chance at adolescence.