All There in the Manual: The art book has a lot of supplemental information about the characters, such as their heights, birthdays/star signs, where they want to travel, etc., and even goes as far as to mention that Yamato has a younger twin sister named Miyako (as far as the game goes, she is nonexistent... but she's set to appear in the Updated Re-release).
The game assumes you played the previous game, therfore assuming you know how the demon summoning program works.
Anyone Can Die: Just like the first game, only even worse. At least one of the player characters dies in any of the endings. About 2/3 of the cast can die, although the game is nice enough to force you to save people after you have failed thrice, so you aren't left with a handful of characters at the end. Worst case scenario, five main characters will die by the end of the game.
Axe Crazy: Bifrons likes to kill humans. He'll always ask the Anguished One if he can kill any humans in sight. The only thing that keeps him in check is his master.
Badass Crew: One mission will have you characters form three of these, and depending on route the Meritocracy, Egilitarian, or Fixed factions will all have one, with the route your main character is on having the most badass of them all at his beck and call.
Badass Longcoat: Yamato and Fumi. A few characters who don't normally wear them have one at least in their possession. In fact, a LOT of characters wear these.
World of Badass: Most humans who have latent spiritual power have access to summoning demons. However, even those that don't can at least fight demons to some degree (as opposed to the first game, where non-demon summoners were boned by default and the only reason demon summoners could fight back at an equal level is because of a special secondary function of the summoning program).
Biodata: Everything is stored as data within the Akashic Record. Including a personas death and the world itself. The Administrator has the power to delete the world or rewrite it using the Akashic Records.
Brainwashing for the Greater Good: Yamato's endgame plan is to convince Polaris to use this to alter the nature of mankind to match his ideal world of merit. Ronaldo, after listening in, derives his own variant of the same plan, substituting merit with equality.
Bittersweet Ending: Sure, the whole "creating a new world from scratch" ending resulting in what appears to be a world of Ghibli Hills is very heartwarming, but you're really going to miss Al Saiduq.
Bland-Name Product: A ruined "Sterbacks" can be seen in Shibuya, and Yuzuru is apparently a reader of "Shoji Leap". And Daichi is into "Aberzombie" apparel. And Joe got scammed into buying an "Armanyo" suit.
While Io is looking for books, you can ask her if she's looking for "Shonen Chump".
A complete list of these can be found here, though in Japanese.
The Blank: Generic JP's members are drawn without a face for a literal version of Faceless Goons. However, they have a face in universe.
Blatant Lies: Grimehkala says something good will happen if you physically attack him. He repels physical attacks.
*Ghost Q summons a bunch of demons to gang up on MC*
Body Surf: Done by Bonus Boss Nebiros if there are any enemies left on the field, and if there's less than 3 present, he uses his turn to make more.
Bonus Boss: Belial, Nebiros, Lilith, Beelzebub, Sage of Time, and Alice are all NG+ bosses, with Alice being the ultimate boss of the game. Ghost Q and Billiken aren't mandatory in sense that if you spend your time elsewhere, you can skip fighting them, but the former expects you to fight him solo with the MC and the latter has several cutscenes dedicated to him. Beating all of them makes them fuseable, although you need to beat Alice to make Belial and Nebiros fusable.
Book Ends: The first battle and the last battle in the game take place at 12:30 Sunday and in two of the six endings the game ends at the same time and place the story began: in the subway just before the train crash.
Kama also suffers a lot of abuse during the fourth day.
Call Back: A very funny one at that. If you manage to defeat both Botis and Bifrons when you first fight them, you get Black Frost to fight you in the 8th Day in all routes except Alcor's. What happens when he moves cements a full Call Back to Devil Survivor...
Black Frost: The messenger of love and justice is here! Time for some magical punishment! ★
Hiro: (Choosing first answer) Frosty!
Black Frost: …Ho? What’re you saying, ho? You got me confused with somebody else!
The message you get from Nicaea after the credits upon clearing the Anguished One's route give another one to the first Devil Survivor.
He doesn't do any such thing in the Japanese version, though, so it's a Woolseyism.
Chekhov's Gun: A event with Joe has him and a NPC mention Billiken on day 2 as a doll and a God of Luck. Come day 6 and said doll is a boss.
A Child Shall Lead Them: In the Meritocracy route epilogue, the group of people earlier seen defending a little boy in one of Makoto's Fate events is being led by him, who the game still addresses as "Timid Boy".
Co-Dragons: Botis and Bifrons both serve Alcor. Defeating both results in Black Frost taking their place in every route but Alcor's.
The Computer Is a Cheating Bastard: Aside from combos on CP demons and humans that would be ridiculous to get, the computer enjoys finding lone characters then juggling them with a ranged demon. A few enemies even get unmentioned buffs such as anti-almighty, or making Strong reduce attacks to 75% damage instead of 50%.
Copy Protection: If the copy protection flags get set off, then during the first boss fight (which starts off as an escape mission then turns into a battle), after the exit is closed off, the event that is supposed to weaken the currently unkillable boss doesn't happen, rendering the game unwinnable.
Deal with the Devil: A website Nicaea, rumored to show images of someone dying in the future, is much more than just that. Anybody who uses the website can form a contract and gain the ability to summon demons and cast spells through their phones.
Death's Hourglass: The Death Clocks and Laplace Mail have been replaced by Nicaea, a website that is able to predict how people will die, but without specifying when or where, which is relevant to the plot many times.
Deconstruction: Like the first game, this game takes every trope Pokémon plays straight and tears them apart. This time, you see first-hand the consequences of a failed demon contract, with a named character no less.
No, you can't kill Dubhe with an Almighty-element attack before Daichi drives the truck into it.
Naming the Protagonist after a plot-relevant character that has six letters or less than their names (either use a first name or a last name) will make the game warn you that another handle is being used with the same name. This is an easy way to tell they are into Nicaea as well.
The game will warn you if you accidentally try to put a leader into battle with no skills.
The passive "Ultimate Hit" makes all your basic attacks almight and changes their name to "Ultimate Hit", the passive Double Strike makes your normal attacks hit twice and changes their name to "Twin Strike". What happens when you use both in the same character/demon? The name changes to "Twin Ultimate", with Double Strike's animation and Ultimate Hit's sound effect.
During the fight against The Dragon Stream, if you get into a skirmish with another demon, you can see its head in the background.
Disk One Nuke: You can learn Ziodyne much earlier than the other -Dyne spells if you crack it from Botis.
Dub Name Change: The races of the Septentriones were changed to Star for the english release. In the Japanese version their race names corresponded with their ancient Chinese name.
Dysfunction Junction: The majority of the cast has a tragic back story of some sort. And those who don't tend to have awful things happen to them throughout the story. There are a handful of characters that have generally happy back stories, like Otome who has recently adopted a daughter. But those can be even more tragic if you really think into it, because now Otome's adopted daughter has to live in a destroyed world.
Early Bird Boss: Botis, should you choose to fight him. Ziodyne and Shield All on Day 3? This Is Gonna Suck. Fortunately, his speed is so low your entire party will get several shots at him before he moves more than once, and with some planning you can easily remove all his Extra Turns to trick it into spending all of his MP while you whittle away its HP. Also becomes a Disc One Nuke if you manage to crack those two skills with a Joint Crack.
Eastern Zodiac: The demons unlocked through fate and the characters personalities tend to correspond with the Chinese Zodiac. Airi for example unlocks Sheep themed demons and Daichi unlocks Monkeys. The only exception being the Anguished One.
The Septentriones have been oft compared to the Angels.
The main trio is initially quite similar to Mikado, Anri, and Masamomi both in looks and personality. But as the gameplay continues, only the similar appearances plays out. Unless the player chooses to make the MC answer like Mikado.
Face Death with Dignity: Ghost Q and Botis on the last day if you didn't kill him earlier in the game when you beat them.
Face of a Thug: Keita, who looks like the previous game's Kaido with light blue hair. Surprisingly, other than him being a bit too rash about things and eager to fight the demons, he isn't that much of a bad guy. To a lesser extent, Jungo.
Failure-to-Save Murder: When you receive Keita's death clip, Joe notes that you could choose not to save him, but wonders if that might not be just as bad as killing him directly.
Family-Unfriendly Death: Several; the first notable one is the train crash on the very first day, complete with shots of bloody corpses strewn all over the place. The Nicaea videos provide more of these examples.
Fan Disservice: Tico (female Nicaea avatar) is physically attractive, but her speech pattern is overly bubbly to the point of Nausea Fuel. Also, her eyes (when open) have a disturbing Uncanny Valley look.
Four Is Death: There are five admins mentioned in the story. Polaris is fourth
Gameplay and Story Integration: In the Turn Back the Clock ending, it is continuously stated that the protagonists will need a "strong willpower" to "keep their memories" after Polaris rewrites the world back at how it was before. Guess how the New Game+ mechanic works?
Gameplay and Story Segregation: During the fight with bonus boss Lilith you have to avoid defeating any of the men under her control or you'll kill them and fail the mission. No reason is ever given for why this differs from all of the fights with civilians or JP's members.
Most likely has to do with them being completely under her control. They are probably trying to fight you to the death. While everyone else fought in the game are in control besides Fumi.
Get Back Here Boss: The fourth day's boss, in more ways than one. It's actually manifesting at several different areas around Japan, so your team has to split up to kill all parts of it simultaneously, plus once you fight it yourself, it keeps moving around the battlefield to evade your attacks. If it takes too long to kill it, game over!
Graceful Loser: Botis in the last day battle against him commends you on having great strength as he dies.
Gratuitous English: The e-mail message you get after the credits is in English even in the Japanese version.
Greed: Billiken's entire motivation during his battle where he hunts down anything that has macca and kills them to get it. If you don't have any he kills you anyway. Even other demons are terrified of him!
Hammerspace: Exactly where does Fumi keep all those laptops?!? She whacks Trumpeter with at least 7 to 10 of em! Her dress is way too small to hold em all...
Hand Wave: Explicitly done on more than one occasion by Yamato about how absurdly prepared JP's is.
Daichi: An exclusive platform...!? Wait a sec, how is this place still running? I mean, after what happened to the subway...!
Yamato: You're wasting time with these useless questions. Let's go.
Handy Remote Control: Practically every weird piece of technology or magic in the game is controllable by cell phone.
A House Divided: By the final day, the party members that are still alive split into three distinct factions concerning what to do about Polaris, and allying yourself with one will cause the party members in the other two to turn against you. However, with the exceptions of Ronaldo and Yamato, you can convince them to rejoin you after the fights if their Fate is high enough. On a certain route you can even get those two to back you up.
Humans Are Cthulhu: One demon, Trumpeter, certainly feels this way after being mercilessly bludgeoned by Fumi.
Trumpeter: "How do I put this... Humans have become such dreadful beings."
Taken literally in that our endless possibilities are able to defy even the fate determined by the Akashic Records.
Ill Girl: Joe's girlfriend. Her condition is much worse than she lets on and she eventually dies. However, it seems as though she's brought back to life in the 'true' ending.
Improbable Age: At a mere 17 years, Yamato serves as the director and leader of JP's. Partly Justified with the explanation that command of the group has been passed down through his family for generations, and they were the ones who founded it. And then deconstructed when it turns out that being treated as an adult from the day of his birth has prevented him from developing a concept of compassion, effectively rendering a low-key sociopath.
Likewise, Otome is a practicing physician at only 24. Not impossible (in Japan, anyway), just unlikely. Fumi is also...some kind of scientist at an age (21) when most people probably haven't finished their undergrad degrees yet.
I'm Taking It Home With Me: Taken to some ludicrous extremes by a Badb Catha when you have to retrieve the pieces of Lugh's essence. If it gets to a piece first, it will squee like a little girl and directly mention this trope.
Interface Spoiler: Even if you don't know the meaning behind the name "Septentriones", an in game event points out said invaders are all named after the stars in the Big Dipper, leading one to believe there will be seven major bosses across seven days. You might then notice the title logo and the file select screen both feature the Big Dipper as well as an eighth star, hinting that the game will not end after a week like the original Devil Survivor.
Invisible to Normals: Dera-deka says that you have to have at least some spiritual power already to access Nicaea.
Interrupted Suicide: Io is constantly afraid of offending anyone, so she always keeps her opinions to herself. However, this turns into an extreme where if you pick the wrong dialog choices, you could end killing her off several times within the storyline. Her main point of character development is when she finds a kid about to commit suicide because he's despairing over his lost family. Io, whose parents were also killed by demons, finally voices her opinion and convinces the kid to live on.
Irony: Abraxas is classified as a fallen demon yet Abraxas talks about repelling evil.
Just in Time / You Are Too Late: Whenever it comes to prevent a predicted death, you will either arrive just as things are getting grim, or immediately after the irreparable has happened. Even the first failed rescue mission is titled "Too Late".
Leaked Experience: Leaders not present in the battle get 80% of what the MC gains (which can be boosted with Watchful and Vigilant). Demons with the latter two skills also get Leaked Experience. On New Game+, it's actually more efficient (especially with the EXP cap removed) to solo as much of game as possible with the MC's team. note With a solo MC, he gets 100% of the available experience and benched humans get 80%. Adding just one other leader reduces experience gains to 50% for the deployed teams and 40% for the benched ones, and it only goes down from there.
Life Drain: The Life Drain skill. Drain does it as well as stealing MP, and Bonus Boss Alice uses a powered up version called Vitality Drain. Which drains HP from every enemy within a range of six.
Lighter and Softer: Unlike the first game, the characters are not locked in one city, so the claustrophobic atmosphere and more explicit decay of society into anarchy are missing. Compounding this is the increase in comic relief scenes and the Fate System allowing for rather sweet and happy moments. The reason for this is that the characters are living comfortably within JP's headquarters and not on the streets. Where the chaos is spreading and affecting the normal civilians who attack JP's in order to get supplies so that they can survive.
Even the covers for the game get in on this. Devil Survivor was dark red and black with the characters illuminated by reddish light. Devil Survivor 2 is blue and white with the characters illuminated by white light and the main character stretching out his hand like a savior.
Darker and Edgier: On the other hand, it takes much less time for the whole world to go to hell, and the sense that time is running out is much, much greater. Also, the lessened exposure to the anarchy of society breaking down is substituted by the knowledge existence itself is literally under attack and its going to get a LOT worse before it gets better.
Literally Shattered Lives: Several times, you'll see some poor human get hit with a blast of ice magic, topple over and shatter. Ouch.
Most notably seen with Merak's Circumpolarity Signature Move in the opening of the battle against him.
You also see a variation of this with fire turning someone to a figure made of ashes that crumble and blow away in Joe's death clip.
Love Potion: Charm inflicts this. Lilith's boss battle has all the other enemies on the field be men she's casted a spell over and her racial skill Temptation inflicts this on men, women, and demons.
Luck-Based Mission: The fight against Yamato. As usual for bosses, he gets an extra turn even while attacking from a range, moves insanely fast (though only two spaces at a time), and even if you can get close, there's a high chance that he'll use Megido twice in a row, which will kill pretty much anything. And of course no weaknesses and Reflect Phys. He also gets even faster as you defeat the demons around him, to the point where even ganging up on him can still end up with him having the faster turn. Even without the double Megido hanging above your head, he has Revive (Recarm on fallen allies at start of skirmish) and one of his demons has Samarecarm.
Magikarp Power: Daichi's stat growth doesn't give him particularly impressive Strength or Magic, making him much less desirable in the first days, where most of the battles are about dishing out as much damage in one blow as possible. Crack Multi-Hit and Multi-Strike, though, and his above-average Agility lets him plow through anything that isn't immune to Physical attacks (though arguably Keita does the same job but better, and Hinako has almost exactly the same stat growth but slightly more fragile).
Make a Wish: Upon being defeated, Polaris will basically grant a wish to whoever defeated him. Each route involves the characters making a different wish. Unless you decide Murder Is the Best Solution.
"The Septentriones" is a name for the stars of the Big Dipper, after an archaic word for "north". They are individually named after each star in the constellation, which is used as a whole as a guide to find Polaris, the north star. And yes, you can look them all up on The Other Wiki.
Mind Screw: Once the Akashic Records start being mentioned, the game then pulls an absurd number of Hand Waves. Said records are actually files for events given for any point in time, and said files have mostly nothing in them and the files with data in them are progressively being erased, which justifies why The Void exists. The records are ancient, and they have been known to record every point in history with incredible accuracy but the Septentriones are the guardians of these records and these records are acting like Laplace Mail in which they are both missing the files for future. However, anyone can give new data for these files, since these files can be edited by Polaris and anyone who controls it, which later becomes the goal for the heroes.
Monumental Damage: Plenty of Japanese landmarks either get wrecked or are shown-to-be-wrecked over the course of the game.
Mood Whiplash: In the Liberator ending, you get a nice somewhat melancholic piano melody that suddenly shifts to the battle theme when the credits roll.
And in the Chaos ending, the picture showing Yamato reigning over the world is a little less dramatic when you notice the protagonist and his bunny ears in the background.
Multiple Endings: Like the first game in the series, there are multiple routes. This time the routes include Ronaldo (Cardinal Ending), Yamato (Mutable Ending), Daichi (Fixed Ending, with three variations including the "True" Ending), and the Anguished One (a very strange ending that could be considered Rebirth). They also have different names each: the person you ally with, a type of star sign, and one of the names listed below. And since Daichi gets multiple endings, the "star sign" names are extended for him.
Liberator. The Kill Polaris Fixed ending is a Downer Ending. The good news is that NOTHING supernatural (good or bad) can ever screw with humanity ever again, and our fate is ours alone to decide. The bad news is that, besides the Void being replaced by ocean, none of the damage done by Polaris has been undone. That means central Tokyo is the only land that exists in the whole world, as over 99% of the Earth's topography is now gone forever.
Restorer. The Turn Back The Clock Fixed Ending has Polaris rewind time to slightly before the erasure of the world, effectively making the New Game+ an in story Justified Trope.
Triumphant. Either of the above endings with all the characters recruited except the Anguished One. The "True" ending is the Restorer + Triumphant ending and gives you a "Where Are They Now?" Epilogue. The heroes vow not to forget one another when the Reset Button is hit. Bits of their Character Development show. Daichi promises to become more mature. Io is bold enough to walk up to you and ask to hang out. Hinako and Airi are getting along well enough to put on a concert together. Keita—who's now a boxer of some renown—is helping Jungo sell chawanmushi. The fear that all the events may happen again is proven invalid when the Nicaea app says that its services are no longer needed and wishes you good luck.
Egalitarian. Ronaldo's Cardinal route involves the creation of a utopia where all men are equal. Polaris' powers accomplish this and the civilians, SDF, and JP's work together to rescue survivors and rebuild society. While the game says that the kind of utopia man dreamed about is created, it questions whether or not mankind can maintain its prosperity without a competitive spirit and the drive to excel. The only certainty is that the future is in the hands of the heroes.
Meritorious. Yamato's Mutable route culminates in the creation of a true meritocracy. Survival of the fittest rules supreme as the weak are oppressed by the strong, and Polaris points out that even Yamato and the Main Character's supremacy could be challenged at any time. On the other hand, creed, color, age and family ties are no longer a bar to individual progress. Those with natural talent or a willingness to improve themselves are rewarded without fail. Demons are also still around this new world. Meaning that humanity must also be careful of demons.
Kingmaker. The Anguished One's route has you defeating Polaris and having Alcor replace him as the world's administrator. The world is reborn with man deciding its fate. Alcor becomes God, but loses his physical form and though the heroes lose the ability to interact with him, they still feel his presence.
Murder.com: Replacing the Laplace Mail from the previous mail is the website Nicaea, which sends out rather gruesome videos of the characters meeting their fated demise.
In the artbooks Otome mentions that Koharu wants to go to Destiny Land.
New Game+: You earn titles based on your accomplishments in the game. Each title is worth a certain amount of points that you can use to buy the right to carry over demons, skills, money, the demon compendium, and auction ratings, remove the fusion limit and EXP limit, unlock Mitama fusion, and to buy the right to battle bonus bosses. Previously unlocked demons stay unlocked, and titles carry over from one replay to the next without having to be re-won.
Nice Hat: Yuzuru's flat cap (overlapping with the rest of his attire), Airi's white pillbox hat, and Jungo's black bucket hat much like Atsuro's hat in the last game.
Subverted. Nobody dies when Alioth crashes into Sapporo. But that's because everyone is already dead.
Averted later when it's implied that there may have actually been survivors who were crushed by Alioth (and if any survived, the deadly toxins that flooded the entire city would ensure it wasn't for long). Yamato just lied so that everyone won't feel bad about leveling the city.
Noble Shoplifter: Done at one point by Daichi and again by Joe towards the beginning of the game. Unfortunately, given just how quickly civilization breaks down, this act quickly become good intentioned but fairly meaningless.
Non-Standard Game Over: If you choose to die rather than live at the beginning of the game. Worth trying at least once to see Tico's dumbfounded reaction.
Not Evil, Just Misunderstood: The Anguished One. He feels that humans are too controlled and wishes to bring freedom back to the world. However, being that he is a Septentrione, he comes off as a villain, and in four of the five routes, you and your party kill him. However, on his route, he becomes the essence of the new world, and becomes a god that loves and respects humans.
Obviously Evil: Subverted. The sprite used for all police officers is downright diabolical looking, with red eyes shaded by a rakishly titled cap and a sneering grin. You don't encounter any actually evil cops in the game; the art assets are just reused from the first game where you do.
One Extra Member: The Septentriones (septem = seven). There are eight of them. The eight one, Alcor, is the only one not presented as a mindless abomination. He is the true identity of the Anguished One. He is the one that created Nicaea so that humanity can fight their fate of being erased from existence. In one of the routes, he even become a party member.
The Only One Allowed to Defeat You: The protagonist and the others were going to be killed by a crashing train; in pops an Obariyon, who holds up the train and cheerily says, "No dying that way! I need to kill you!"
Oo C Is Serious Business: Pretty much all of the characters, if you develop fate with them. Io expresses her true thoughts, Daichi gets over his cowardice and attacks demons voluntarily, Joe foreswears being late ever again, Keita saves his teammates, and Fumi stops her experiments to save Jungo (or Daichi)'s life.
Ignored Epiphany: Unfortunately, while these scenes look more like Character Development than OOC behavior, the apparent changes do not carry into main story sequences. Ronaldo and Makoto are hit particularly hard by this.
Interesting not in the fact the themes are present, as they are a Mega Ten mainstay, but in the portrayal which follows astrological star sign qualities (Cardinal v. Fixed v. Mutable) than the traditional split. Both the "Law" and "Chaos" factions rely on Polaris to brainwash humanity to follow their plans of perfect egalitarianism or a hierarchy based on social darwinism (a Chaos mainstay for the series), and Polaris seems to favor the "Chaos" faction more than the "Law" one. All three factions are presented as valid points of view but both "Law" and "Chaos" arguably have terrible spokespersons.
Oddly, though a possible Neutral/True Freedom/Chaos variant provided by the Anguished One is a weird mix of the freedom of Chaos and a entity who watches over us and will never interfere with us unlike past Law figures(and Polaris himself.
Parking Garage: A recurring random battle map, the site of a very violent confrontation with Jikokuten and the site of Dera-Deka's death.
The Peeping Tom: in the "Secret Garden" cutscene, Daichi and Joe decide to spy on the female cast members' physical exam. The main character can join them too, leading to an eavesdropped conversation of the girls comparing their "assets," and several minor What the Hell, Hero? moments later on.
Post-Modern Magik: Traditional demon summoning rituals are transformed into a cell phone app.
The Power of Friendship: Similar to social links in Persona 3 and Persona 4, this game will have the 'Fate System' which allows you to form bonds with other Devil Messengers, which in turn helps them unlock new elemental strengths, special abilities, and new demons.
Also, only characters with at least Stage 4 Fate will agree to rejoin you in the final day except Yamato or Ronaldo if you pick one of their opposing sides or Alcor's route, but you can have them both in Daichi's routes. Ronaldo even ends up helping you persuade Yamato into joining you.
Mentioned word for word during the final battle with Polaris during Ronaldo's route.
Punny Name: In the manga adaptation, the main character is given the name Hiro Kageyama.
Rage Against the Heavens: What Alcor's route boils down to: You overthrow the administrator of the world and create a new world without it.
Red Shirt Army: The gold-uniformed JP's members don't even have eyes in their facial portraits, so it should come as little surprise that they get killed by demons and Septentriones. This is deconstructed by how little their Social DarwinistBad Boss cares. Yamato only cares about the successful; dead subordinates are incompetent ones.
Screw Destiny: A major plot point of the game is that the past and future are already written. However, you spend most of the game giving this concept the middle finger and saving people and reality itself from their so-called destiny.
If you defeat all the demons before defeating Ghost Q he'll decide to run away and must be beaten before he escapes to unlock him.
This is also Kama's reaction to learning what the cast wants him to do.
Sequel Escalation: Overclocked additions included three new playable days and the most voice acting out of any Atlus title produced at the time. Break Record is set to trump this with the addition of an entirely new, seven day campaign.
Shout-Out: To Metal Gear when Io sneaks in using a box as a disguise during the mission where you rescue Daichi.
The Stoic: The main character. Unlike the previous game's hero, who could get pissed off/startled, DS2's rarely shows any emotion. Even his usual angry/battle-ready pose has the same neutral expression as his default pose.
Bonus Boss Beelzebub entire reason for being a boss fight. He's heard great things about the Protagonist and has come to test that strength.
Bonus Boss Belial and Nebiros picking the player characters to be Alice's friends is because they are so strong that they are worthy of being her friends.
This is also how Alcor tends to test people's worth. Such as the last day battles against one of his three Dragons.
And of course, this trope is related to why Yamato takes a shine to the MC after the party beats Dubhe as well as why he fights the MC (to "wake him up") in routes other than his as well as why Defeat Means Friendship for him in Daichi's route. He did sincerely believe Might Makes Right, after all.
When pitted against the choice between Yamato's meritocracy and Ronaldo's egalitarianism, Daichi chooses to instead seek for an alternative solution that wouldn't harm anyone. And even though he doesn't have a clue on how to do it, he still convinces Hinako, Io, and Jungo if he's still alive to follow him.
Then, the Hero can further take a fourth option by not joining any group and convincing the Anguished One to overthrow Polaris.
ˇThree Amigos!: Notable in that the Protagonist and Daichi didn't meet Io until the beginning of the game. In the "true" ending, it's hinted that this is their future as well.
Though in addition to Tokyo, you also get to visit Osaka and Nagoya. Sapporo and Fukuoka too.
Taken more literally in the Liberator ending where it's essentially all that remains of Earth and its landmasses, the rest of it taken up by the Void being replaced by an endless ocean.
Two Guys and a Girl: The protagonist, Daichi and Io. Sort of subverted by Joe, who joins the group not too long after they summon their demons, and acts as a fourth to the group even though he was mostly excluded in all the promotional material for the game. "Sort of" because he's not really a peer in their age group and isn't seen with them in the "true" ending.
Ungrateful Bastard: As soon as you beat Billiken, the demons he was attacking decide that he was on to something and proceed to attack you for your Macca.
Vaporware: Not the first game but its remake. It has fallen into obscurity about its progress ever since a year ago of its announcement.
The final boss also uses one that covers the only path to reach his core in the third phase of his fight. It also hurts like crazy, but you get plenty of fair warning it's about to happen.
Western Zodiac: Aside from the Main Character, the Anguished One, and the Ticos, an artbook have stated that each of the characters represent one of the twelve signs of the Zodiac. The elements of each sign with Electricity replacing earth usually shows up as a resistance for each character at Fate 1, though there are exceptions. Their birthdays also match their respective zodiac sign.
The characters gender is also determined by their sign. As positives are male and negatives are female.
The characters routes, with possibly the exception of Daichi's Liberator and the Anguished One's Kingmaker are based on the Qualities of their Star Signs. Daichi's is Fixed, Yamato is Mutable, Ronaldo is Cardinal, and the Anguished One possibly represents Rebirth since the world is remade.
As a side note, During the Faction Warfare, only Daichi's team has one of each elemental Zodiac sign
The Protagonist and Anguished One not having any zodiac signs themselves leads to fan speculation that they are the 13th Sign Ophiuchus. A long time later, it was revealed that the protagonist is actually Gemini, which would of course be the only sign there were two of.
World of Buxom: Every playable female character is notably gifted. (Yes, including the Token Mini-Moe, who is average at worst.) However, this is only really true of their conversation portraits. All are more modestly drawn in the few video cut-scenes and in their battle sprites.
Your Days Are Numbered: Every day starting on Sunday one Septentrione attacks Japan. Because the alien invaders are named after the stars in the Big Dipper constellation, Hinako speculates that there will be a total of seven Septentriones, with the attacks lasting a week. And according to Yamato the Septentriones have the ability to destroy the entire world.