One of the main characters in the Moyashimon franchise.
Kei Yuuki is a university student and a childhood friend of Tadayasu Sawaki, who he later reveals to have strong feelings for. He and Tadayasu initially go to agricultural university together, but Kei soon takes a leave of absence. Upon meeting Tadayasu again, he reveals his feelings for him and his own gender dysphoria. In the anime series he is voiced by Mitsuki Saiga.