
Quick answer — OxT performed 5 anime themes, including "Clattanoia" from Overlord, "HOLLOW HUNGER" from Overlord IV, "Silent Solitude" from Overlord III.
OxT performed the anime theme songs "Clattanoia" (Overlord), "HOLLOW HUNGER" (Overlord IV), "Silent Solitude" (Overlord III), "UNION" (SSSS.GRIDMAN), "One Hand Message" (Hand Shakers).
OxT's first listed anime theme is "Clattanoia", the opening of Overlord.