A Selcom is technology existing in the A3W world that acts like a computer inside people's brains. People can chat with friends in virtual rooms and play games while focusing on other things in the real world. Selcom usage is tied with P3 levels, as higher levels means you can use a Selcom more easily due to the stress it puts on the brain.
Selcoms have had much technology and apps developed for it, but the most popular is Kizuna, which allows you to easily form friendships with others. Kizuna also comes with Keropoyo, an AI.