夏休み満喫用忍び装束
Broken down it's literally "Summer Vacation (夏休み) Fully enjoying (満喫) for purposes of (用) shinobi costume (忍び装束)."
It is not easily translated into something that flows well, so I would personally wait until the major fan sites settle on something before tagging it, and just go with what they use unless it sounds downright horrible.
edit: Seems to already be tagged shinobi attire for summer enjoyment though, which I guess is fine.
