Oh the Deja Vu…
A great enemy approach the main characters for one particular female member's sake. After the conflict said female member decides to leave group despite her friends fought tooth and nail to protect her, in order to save them from further trouble.
Nico Robin round 2 much?
Except, in OP's case, the SHs got wtfpwned by Aokiji in the first conflict, justifying Robin's fear and eventual departure. The short confrontation served as a nice prelude to the upcoming epic rescue arc.
Here in FT, the Fair Tails spend an entire arc saving Lucy from Phantom and actually won, yet she still decides to abandon her friends and go home? I guess all the "pain, laugh, tears" they shared togather was, afterall, not enough yet. It almost makes this past arc seems pointless plotwise.
It's equivalent to Robin leaving AFTER the W7/EL arc, totally retarded IMO.