How to get into floor 16 of mushin tower?

[Montgomery]

I finished 1-15 but it wont let me do floor 16 Idk which npc to talk to, or if its a quest letter what is the name of it?

[SkyStorm]

There's "Two against one" that you get from Dokdan and "A raucous reunion" from Podan. Also, "The dead refuse to die" but I can't remember who gives that.

 

Should be one of those I think.