Kimi is the frivolous, androgynous facet of Shibuya, one of the many personalities into which Shibuya splits, along with Jequima and the executioner. Kimi is the light face that flirts and chats, and the one that made contact with Zaa in the redoubt.
When things turn serious, Kimi puts on the kendo helmet, and from behind the mask comes no longer Kimi but the executioner.