Quick answer — Mika Nakashima performed 1 anime theme, including "Inori, Owareba" from Mushoku Tensei: Jobless Reincarnation Season 3.
Mika Nakashima performed the anime theme songs "Inori, Owareba" (Mushoku Tensei: Jobless Reincarnation Season 3).
Mika Nakashima's first listed anime theme is "Inori, Owareba", the ending of Mushoku Tensei: Jobless Reincarnation Season 3.