Boku no Gemini

Plain, redheaded, and freckled John has nothing going for him, except his two friends who are incredibly popular at school—twins Jekyll and Hyde. The twins, indistinguishable, have always enjoyed taking each other's places for fun. But when the pair is fragmented by an untimely death, it's up to John to find out…which twin is left? 

(Source: Yen Press)