Quick answer — Yoko Takahashi performed 4 anime themes, including "A Cruel Angel's Thesis" from Neon Genesis Evangelion, "Kanon in D-Dur" from Neon Genesis Evangelion: Death & Rebirth, "Yoko Takahashi - Soul's Refrain | EVANGELION: DEATH" from Neon Genesis Evangelion: Death & Rebirth.
Yoko Takahashi performed the anime theme songs "A Cruel Angel's Thesis" (Neon Genesis Evangelion), "Kanon in D-Dur" (Neon Genesis Evangelion: Death & Rebirth), "Yoko Takahashi - Soul's Refrain | EVANGELION: DEATH" (Neon Genesis Evangelion: Death & Rebirth), "Metamorphose" (This Ugly Yet Beautiful World).
Yoko Takahashi's first listed anime theme is "A Cruel Angel's Thesis", the opening of Neon Genesis Evangelion.
