Moshimo, Yuurei ga Hatsukoi wo Shitara.

I'm Sota. No romantic experience, just your typical nerdy, socially awkward high school boy... or at least, I was. Wait, you're wondering if I lost my virginity and became a popular guy? Nope, not even close. I'm not a high school boy anymore—I'm a ghost. That's right. I went from being a socially awkward, nerdy virgin to... well, a former human ghostly virgin. I don't remember much about my previous life, but the one thing I do know is that I died a virgin. Yeah, I'm pretty sure that's my unfinished business. To make things worse, I can't leave this all-girls' school, so now I'm stuck as a spirit, wandering the halls like some kind of low-tier ghost. At first, I thought it wasn't all that bad—since I'm invisible, I get to see the girls in ways I never dared dream of when I was alive. Not gonna lie, I felt a little guilty, but hey, being a ghost isn't that bad! Then one day, I noticed a keychain of my favorite anime character lying on the floor. When I tried to pick it up—"Why is there a boy in our school?" That's when I met her—a cute, kind, and popular girl who's friends with everyone. Somehow, she's the only one who can see me, the ghost that I've become. And to make things worse—or better—I think I've fallen for her, a girl who's totally out of my league... (Source: Manga Mirai)