Shoichi Kusanagi - He's hacker like Yusaku and hacker rivals.
Naoki Shima - Probably is trying to be Yusaku's friend, but he's mean... (My predictions)
Akira Zaizen - Probably Aoi's brother...
Ema Bessho - No idea... Maybe Yusaku's fan girl xD
The first episode is named: My name is Playmaker
VRAINS means Virtual Reality Artificial Intelligence and Network System
Well, for now we'll wait the first episode ^^