D・N・ANGEL

Daisuke Niwa is a 14-year-old middle school boy who is clumsy, cries easily, and feels unmanly. On his birthday, he confesses to his crush Risa Harada but gets rejected for not being masculine enough. Strong romantic feelings trigger his transformation into the phantom thief Dark Mousy, a tall, confident alter ego with long black hair. Dark begins stealing specific art pieces linked to his family's legacy. Meanwhile, classmate Satoshi Hiwatari pursues the thief, and Risa develops admiration for Dark after seeing him, while her twin sister Riku starts noticing Daisuke's kinder side. (Summary by Grok 4.1)