Saeko is a name used by several fictional characters, but the best-known one is Saeko Busujima from Highschool of the Dead. Another well-known Saeko is Saeko Nogami from City Hunter.

Most likely answer

  • Saeko Busujima → Highschool of the Dead
  • Saeko Nogami → City Hunter
  • Saeko Takami → the Persona series

If you meant a specific Saeko, that title depends on which character you saw.