Touko Yonera 米良 柊子 (Yonera Tōko)
Touko is a 27-year-old doctor in the psychopathology lab at Tachibana General Laboratories, born in Setagaya, Tokyo, and recently back from graduate study in the United States. Lain is her first patient. Her own voice diaries and notes make up a large share of what the player unlocks, so the game is as much her story as Lain's: her stress at work, her longing for her boyfriend Takeshi, who also works at Tachibana, and her slide into instability when she learns he is marrying someone else. Ueda told 4Gamer that Konaka probably created her setup, and both remembered Tachibana Labs as Konaka's invention. Maya Okamoto voices her.
More (spoilers)
As Touko comes apart, Lain turns her growing knowledge of psychology on her therapist. Ueda describes the arc as the hunter becoming the hunted and wondered whether horror had done that before; Konaka thought it might be original. Touko's collapse feeds directly into the game's violent end. Her failed relationship with Takeshi, which she records in growing despair, is the thread the player follows alongside Lain's own.
▶ hear Touko in the game: 269 files
Sources: ja.wikipedia.org archived · en.wikipedia.org archived · 4gamer.net archived · 4gamer.net · lain.wiki · lain.wiki