
Quick answer — Konomi Suzuki performed 8 anime themes, including "Realize" from Re:ZERO -Starting Life in Another World- Season 2, "Redo" from Re:ZERO -Starting Life in Another World-, "Reweave" from Re:ZERO -Starting Life in Another World- Season 3.
Konomi Suzuki performed the anime theme songs "Realize" (Re:ZERO -Starting Life in Another World- Season 2), "Redo" (Re:ZERO -Starting Life in Another World-), "Reweave" (Re:ZERO -Starting Life in Another World- Season 3), "Theater of Life" (DECA-DENCE), "Utaeba Soko ni Kimi ga Iru kara" (LOST SONG), "Beat your Heart" (BBK/BRNK), "Chaos Syndrome" (Chaos;Child), "PROUD STARS" (Shin Ikki Tousen).
Konomi Suzuki's first listed anime theme is "Realize", the opening of Re:ZERO -Starting Life in Another World- Season 2.