Tezuka's first appearance in the series is as a minor character in a short story in The Case of Takafumi Yokozawa 3. He is charge of merchandise at Animate, and Takafumi Yokozawa has worked with him since he was first assigned manga sales at Marukawa Publishing. Yokozawa is visiting a new Animate branch in Ikebukuro when it starts to rain and is caught without an umbrella. Tezuka comes into the new store just as Yokozawa is leaving and offers him the umbrella he was just using. Yokozawa declines since then Tezuka would be without an umbrella, but Tezuka says he'll just take Saigusa's umbrella, and he teases Saigusa that then he could just have his girlfriend pick him up. Yokozawa accepts his offer to borrow the umbrella, saying that he would return the umbrella when he next visited the store.
Tezuka's relationship with Saigusa is explored in the novel The Case of Animate.