After Kayleigh's death, he took Kevin in to raise him alongside Riko. He didn't adopt him, but gave him to Riko as property. Due to all the money and time invested in Kevin, he sees all of the profit he generates as his family's.
Tetsuji is a member of the Moriyama branch family. His brother, Kengo, heads the main family and their criminal empire, but because he was not the first-born, he is relegated to the branch family. This excludes him from the family business but gave him the freedom to study in Japan and make the Ravens the best Exy team of the nation.
Tetsuji had the Ravens transfer districts to cash in on Kevin's status as Exy champion for as long as it lasted. He planned to pit him against Riko so he could finally show that Riko was the superior player.
Raven players call him "the master".