Talk:Christmas 2013 Event/@comment-124.209.126.151-20131226065520/@comment-1482018-20131227010744

Whoa, chill... MB1 says the following (from the link the anon provided):

MB1: 謎の潜水艦「イオナ」と接触せよ (Sink an enemy sub) It's actually 2 subs by the way. This quest should be the very LAST quest among the sortie quests.
 * Easiest submarine battles are in 4-1 or 4-2. Newer admirals who have not unlocked World 4 can find submarines in map 1-4

http://kancolle.himeuta.net/forums/viewtopic.php?f=16&t=124&p=1796

See if this helps with anything.