Below it, a download button appeared. Not for the PDF. For something else. The label said: "Kenji_no_kioku.pdf" — Kenji's memory.
By page ten, the sentences grew personal. "Kenji-san wa mainichi nani o shite imasu ka?" (What is Kenji doing every day?) He hadn't entered his name anywhere. He typed: Benkyou shite imasu (I am studying). The PDF responded: "Hontou desu ka?" (Really?) The text changed color—from black to a deep red.
Page twenty. The exercises became commands. "Kenji, kuruma o mite. Soko ni dare ga imasu ka?" (Kenji, look at the car. Who is there?) He glanced out his window. No car. Just an empty street. When he looked back, the PDF had added a new line: "Mada minai de. Yokatta." (Don't look yet. That's good.)