Kuro

Kuro is a junior high school student who works as Ramune's assistant. He has good judgment and motor skills as well as a rational mind. It's hard to understand his mood due to having a poker face and is always having to play the straight man when Ramune says or does anything. Kuro trusts Ramune's skills as a specialist of mystery diseases completely. He has a rational mind and strong judgment.

(Source: Official Site)