Talk to Furou at [X:3700, Y:1050] and agree to help him propose to Mabel.
Follow him into his house [X:3820, Y:935] and talk to him again. He tells you to wait for him at the northern area of Africa Plain.
Go to the Africa Plane [X:450, Y:1192] and then to the northern most part of this area [X:3250, Y:535] where you will see Mabel being attacked by lions.
Fight the lions [Lion, LVL:85-86, HP:900-1010]*3 with Furou. After the fight, Furou propses to Mabel and you get your reward.
