The Deepsea Metro runs along ten lines, denoted by the letters A to J, each containing stations that make up the Expansion's levels. There are a total of 85 stations, including eighty mission stations, four thang stations, and Central Station. 22 of the mission stations are exchange stations, connecting two different lines of the Metro. When Agent 8 completes an exchange station's mission for the first time, the connecting line is revealed and C.Q. Cumber gives them CQ Points as a reward.
I'm pooped, Agent 8. Gotta rest my cuttlebones here for a bit.
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You gotta be squiddin' me! A talkin' sea slug?!
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That's right! We want out of here!
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So all we gotta do is pass some tests and find some thangs and we can go home?
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Oho! What in the blazes?! Technology these days...
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After clearing Fake Plastic Station:
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Huh... Is this thing working?! Oho! I hear something! Come in, Agent 3! Agent 3, do you copy?!
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EXCUSE ME?
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Hwa-?! Who am I speaking to? Where is Agent 3?! State your names!
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Oho?! Check it, kid. Are you stepping to me with a rap battle? MC Craig in the house! Call me Cap'n Cuttlefish, but not because I cuddle with fish. Smooth like butta bet you wish that you could stunt a flow like this!
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Mount Nantai... Why that's near Octo Valley! Agent 8 and I were near there, but someone seems to have taken us deep underground...
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OK, well... Anyone who loves rapping is a friend of mine. Thanks for your help! We're off to pass some sorta tests and make our way to the promised land! And by "we," I mean you, Agent 8! Time to get after it!
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After Iso Padre comes aboard:
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Not sure this Iso Padre is playing with a full deck... Doesn't seem like a bad chap, though.
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After defeating Commander Tartar:
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It's been a while, Agent 8! Glad to see you're still alive and kickin'! I got curious how things were down here... And you know, this place has grown on me! Where's who? Oh, Agent 3 had business to finish up and headed out back on patrol! If there's anything you've got left to do down here, I'll be glad to offer my support!
Thank you for using Deepsea Metro today. I am your humble conductor, C.Q. Cumber.
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Pardon me? I take it this is your first time riding with us... Here's the deal... We're in a vast underground facility operated by the Kamabo Corporation... It's a series of test chambers connected by the Deepsea Metro subway system. I see that you're in possession of a CQ-80 device. I take it your aim is to reach the promised land?
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Understood. The promised land is a paradise to which we denizens of the depths are forbidden entry. To reach it, you must pass a test at each Deepsea Metro station. You must also find and collect the four thangs. When all four thangs have been gathered, the door to the promised land shall open.
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I believe so... Let me show you to your first test. Press to activate your CQ-80.
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This is the Deepsea Metro map. Go ahead and select a destination.
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That's central station, where we are now. Try selecting the station above.
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Very good. Now departing for the first test.
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After clearing Fake Plastic Station:
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Congratulations... You passed your first test. By the way, you received this memento when you finished. It's called a mem cake. Mem cakes are formed by compressing memories into physical form. They'll be awarded to you by Kamabo Co. to commemorate each test you pass. Use and in your CQ-80 menu to check out your collection of mem cakes. New stations are now available for you to visit and test your skills within. You can move freely to any station with a ⚫. Safe travels...
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After defeating Commander Tartar:
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Number 10,008, nice to have you aboard. We applaud all of your previous efforts. It seems you've safely achieved your goals. Unfortunately, Kamabo Co. is in disarray... But thankfully, Deepsea Metro service has continued without interruption. All we do, we do for the satisfaction of our customers... Please allow me to announce a new service that we have just begun to offer. This service allows you to exchange CQ points for items. We have a nice selection of premium offerings that should prove quite useful. This service is available at Deepsea Metro Central Station. I encourage you to stop by. This brings my announcement to a close... Safe travels, my friend.
Uh, I think I asked you first, dude. Anyway, I'm Pearl, but you can call me MC.Princess! My deets? I'm short and sweet! I spit that fire make posers perspire. Step to my game? I'll bring the pain. I'm never shook because I'm OFF THE HOOK!
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I don't really get what's going on, but hang tight. We got you!
Pearl! Didn't anyone teach you to respect your elders?!
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OK, you two... That's ENOUGH! Mr. Cuttlefish, was it? We found a radio here and heard your transmission. We're currently on Mount Nantai. Where are you calling from?
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I see... So you and this...Agent 8 don't know where you are? Sorry to hear that... But worry not! From now on, you'll have me, Marina-aka DJ_Hyperfresh, supporting you! I'll get to work analyzing your surroundings, and hopefully I'll be of some help to you!
Beg your pardon, young squire. Might I have a look at those trinkets you've got there? Forgive me if I caught you off guard. (Hope I'm not too off-putting for the child.) They call me Iso Padre. That's not my name, mind you, but it's the only one I recall now. Down here, we call those thin slices of memory mem cakes. I've spent an age or two in the depths, hungry for them. They're my only link left. (At least I still remember my own days as a test subject...though I washed out early.) I pray that you'll be the one to cut through the gloom and light the way to my dreams. Share your mem cakes with me, and I'll repay the favor. Safe travels, young squire.
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After completing one Mem Cake set:
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Wait. Let me make sure I understand you right. You completed a whole series? That's special. That's something else. I always wanted to see a full set.
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After completing two Mem Cake sets:
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Two full sets now? Young squire, you've outdone yourself. I'm not much of a teacher, but if I was, I'd give you an A for effort.
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After completing three Mem Cake sets:
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Well now, have you finished up a third set? May wonders never cease. I see you know the way through this thick, old carapace right to my heart.
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After completing four Mem Cake sets:
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A fourth set? Every one? Once you get your sights on something, you don't stop. And why should you, when your dreams are in sight? Eyes on the prize, young squire.
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After completing five Mem Cake sets:
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Five sets already. Where does the time go? You've come so far, and we've only just met. I was saving this for a special occasion, and I believe now qualifies.
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After completing six Mem Cake sets:
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Your collection grows, I see. Six complete sets is mighty fine, no bones about it. I like to see you apply yourself. Does a world of good for my own dream.
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After completing seven Mem Cake sets:
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Seven series. I never thought I'd live to see the day. Maybe I should dream bigger. Don't ever give up on your dreams, young squire, or they might give up on you too.
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After completing eight Mem Cake sets:
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Eight series now. That must give you a little thrill, right? Eight's an important number. I wish I had an eighth of your tenacity, young squire. Alas.
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After completing nine Mem Cake sets:
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You're only one series off from a complete collection of mem cakes. Yesterday's so close I can almost taste it. Bring us back those last few slices.
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After completing all Mem Cake sets:
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Well now. A full, unbroken set of mem cakes. You're living the dream. Suppose the flip side is I won't see much of you anymore. Shame, that.
With exchange stations having two numbers, one for each of the lines they connect to, the first number is always backwards alphabetically. For example, Girl Power Station is denoted J03D08 (and not D08J03) because J comes after D in the alphabet.
The mem cake for these stations is always from the series of the latter letter line as well.
The music played in the subway train has a few notes of the Calamari Inkantation played in the background.
More notes are added as Agent 8 gains access to more lines. After clearing the game, the complete track containing the main melody of the Calamari Inkantation is played.
According to sound director Minegishi in a Famitsu interview,[1] the Calamari Inkantation can be constructed as Agent 8's auditory hallucination, an inner melody of their mind that intensifies as more of their memory returns.
A poster advertisement of a video game console, resembling a Nintendo Entertainment System, can be seen in the subway train.
Deepsea Metro can be construed as a homonym of the D.C. Metro.
to activate your CQ-80.
and 
in your CQ-80 menu to check out your collection of mem cakes. New stations are now available for you to visit and test your skills within. You can move freely to any station with a ⚫. Safe travels...
