[sarasi]

Only some trains go straight to Ikebukuro, and you might have to wait a long time for one. Unless there is one departing soon after you get to the Arrivals hall, it may be better to either take the bus, or take the NEX to Tokyo or Shinjuku and then the Yamanote line (not the Metro which is the subway and means you would have to buy another ticket) to Ikebukuro.

If you are arriving around rush hour then I recommend the bus if there is no direct NEX to Ikebukuro at that time, because commuter trains like the Yamanote line are no fun in rush hour with luggage.