姉街 (Anemachi)
meganekoexHoshimachi Suisei (星街すいせい) 's Sister
Anemachi (姉街) is Suisei's older sister who can sometimes be heard in the background of Suisei's streams, and both of them are seen to be very close to each other. Anemachi and Suisei voices are very similar, so much so that sometimes it's hard to tell who is talking when they are chatting. (src: hololive fan wiki)