Boku no Gemini

Shy, bespectacled John Utterson is the only person who can tell the popular Stevenson twins apart. This achievement is even more impressive considering that the cool and composed Jekyll and the cheerful and expressive Hyde purposely take turns pretending to be each other on a regular basis. However this game of theirs began, it has been going on long enough that the once distinct lines between their true selves have faded; if they are always together, it does not matter what role the two play. But when one of the twins dies in an unfortunate accident, they can no longer be called "Jekyll and Hyde," and even John has to question which of his best friends survived.