Toremororetora

Kazura has her first high school boyfriend, a cute guy named Iwasaki who likes her very much. When he takes her to see her favorite band perform live, she meets the band's cool, attractive vocalist. The next day at school, she discovers a secret: the sexy vocalist is none other than her teacher, who seems totally uncool in his daytime appearance! What will she do about her boyfriend, her teacher's secret, and her growing attraction to him? (Source: MangaHelpers)