Survival Mode Floor 71+: Transport Rescue. But there's a prerequisite.
In order for this mission to appear in survival mode, you first need to complete a mission called "Medicine Hunt" on any floor it appears in. So anytime really, but the sooner the better. But on the same session you clear that mission, you can get this one to show up.
Once it does show up, you want to make sure that you bring either a powerful character, or some beneficial skills to help you do damage and survive. In my case, I used a Shrine Maiden and managed to get some extra White Swords (Attack X2) while she provided enough life to survive on low health. The whole mission is about the Fūma Treasure and how much a lot of people want it. With all this greed... kinda makes you wonder why this doesn't unlock Greed 4...
71F deals with raiders. Well you already saw my rant on these fools before, so you shouldn't have any trouble here. Take them all out and move on.
72F Has you dealing with a Hyper Magoroku Saika. He doesn't have the treasure but he's in your way. deal with him and head up the stairs.
73F Involves Magoichi Saika. He won't hand it over because he wants to give it to Okuni. Well clearly that's not going to happen. He's in Hyper Mode, so pull out all your tools on him.
74F Has Okuni demanding that you give her the treasure you just got. Though she's weak, she's so ambitious that she'll reappear two more times-- the second with Hyper Magoichi again. I have not Awakening 3, but it's still quite a grind to beat them both. Be careful of the Miscreants.
And then 75F. Kotaro Fūma would like that treasure back... probably to promote more chaos no doubt. But that's not all. Hideyoshi, Nene, Mitsunari and Sakon all appear at the upper right of the map to attack you afterwards. This is the hardest part of the mission, and if you don't have a good trick up your sleeve, it will prove to be a difficult fight.