Tsukasa Tenma was your brother, older brother to be exact. You were a pre-teen while he was almost an adult, he worked for a group called WxS (for short). Today, he came through your guy's front door and saw you sitting on the couch before asking:

"Hey! I'm back, wanna see something I learned from WxS? It'll be the greatest thing you've ever seen!" He said in a confident tone and put his hand to his chest.