While out adventuring in her Crapsack World, IF comes across the Great Library, said to contain records on the history of the world. At the same time, a girl (Segami) falls from the sky and is saved by IF. Inside the library itself, the two learn from this world's Histoire that history is disappearing, and thus the two team up to travel back in time to determine the cause. IF trys to avoid creating a paradox, while Segami is a little more open to the idea of rewriting history...
The game provides examples of:
- Adaptation Dye-Job: In the European release, to match how the console she's based on had a different logo in that region, Dreamcast's outfit is mainly blue instead of orange.
- After the End: The present time, with most things in ruins, blackened lands, pretty much no vegetation, and not much in terms of culture present, going by IF's comment. The long, constant battles between the Goddesses and the Hard Girls really does a number on the world, which could be seen clearly when traveling between different eras. In fact, this version of IF had never heard of Goddesses or the Hard Girls at all until she traveled into the past.
- Alien Geometry: The portion of the Grand Library that the Time Eater is destroying is this, if the background art is anything to go by.
- Ambiguously Lesbian: Segami. She gets excited when bike Nep jokingly tells everybody that IF was planning a getaway between herself and Segami, then is visibly upset when IF immediately denies it and points out that any trip they take would automatically include bike Nep out of necessity.
- Amnesiac Hero: Segami comes falling from the sky with no conscious memories that she can recall. She'll only fully regain her memories in the True Ending.
- And the Adventure Continues: Once the Time Eater is defeated, IF leaves the library to explore the world some more. In the Normal Ending bike Neptune joins her, and in the True Ending everyone returns to play.
- Anti-Frustration Features:
- Need to know where a specific monster or drop can be located? The Quest menu includes a search option that reveals where the particular monster/item can be found, provided the player has at least unlocked said dungeon.
- A late game Plan has successful Symbol Attacks instantly end the fight and grant full experience, credits, items, and some Lily Rank points if the player is sufficiently higher level than the enemy, which greatly cuts down on grinding near the end of the game and in NewGamePlus.
- If you get the Normal Ending, you have the option to go back to before you fought the Time Eater, so you don't have to start all over or have another save ready.
- Artistic License – History: Used In-Universe as a way to explain how the Game Gear era came after the Sega Saturn era rather than the Mega Drive era (and to prevent Nepgear from becoming Neptune's older sister as a result).
- Notably, this is the ONLY Neptunia game to address the paradox!
- Beach Episode: Part of the True Ending.
- Berserk Button: What's the fastest way to incur IF's wrath? Damage or tamper with her bike.
- Big Bad: The Time Eater.
- Big "NO!": IF's and Segami's reaction to being Iris Heart's next plaything.
- Bitch in Sheep's Clothing: Segami, who's shown trying to prevent "useless" battles from happening, without caring why they're happening in the first place. Although, she does get better later on in the game.
- But Now I Must Go:
- Segami in the True Ending. Subverted in that she returns to go on further adventures with IF almost immediately.
- All of the goddesses and Sega Hard Girls have to return to their respective eras in both the Normal and True Ending. Until they all get bored and come to IF's era to play after a couple days in the True Ending.
- Butt-Monkey: Neptune gets the short end of the stick in this game. Her body is erased from time not too far in, she merges with IF's bike, and neither IF nor Segami treat her well.
- Can't Drop the Hero: Either IF or Segami must always be in the active party.
- Can't Take Criticism: When IF and Segami told Neptune that she's weak, Neptune doesn't take the criticism well because she likes to think that she's the ultimate protagonist.
- Cargo Ship: In-universe, when Nepgear meets bike Neptune and learns that they're sisters, she wonders which of their parents is the bike.
- Class and Level System: A class system is introduced in this game, which levels separately from character levels. Each character has access to different classes, e.g. IF's Nomad and Noble Thief and Segami's Hammer Lord and Virtuoso.
- Class Change Level Reset: Every class has to be leveled up independently and starts at Level 1.
- Cool Bike: IF's bike is quickly turned into a time machine! However, soon after it becomes inhabited by Neptune's spirit and IF is devastated by the new color scheme.
- Demonic Possession: Both Sega Saturn and Iris Heart have to be fought while possessed by the Time Eater.
- Double Entendre: Bike Neptune even Lampshades it whenever she talks about the other girls riding her. That includes talk about being ridden by her non-bike self.
- Dual Wielding: Sega Saturn dual wields staves.
- Earn Your Bad Ending: To get the Bad Ending, you have to defeat the Time Eater the first time you face it. To do so either requires a massive amount of grinding on your first playthrough or fighting it in New Game Plus with a sufficiently leveled party.
- Eldritch Abomination: The Time Eater.
- Friendly Enemy: Nepgear and Game Gear are this with each other, as they have no desire to actually fight. They're drawn into battle when their supporters- who are possessed by the Time Eater- rally both sides into a frenzy.
- Generic Doomsday Villain: The Time Eater has no motivation beyond simply wanting to devour all of history via causing the Sega Hard Girls and Goddesses to fight each other until all the world is a wasteland.
- Gotta Catch 'Em All: Collecting all of the medals in each dungeon and all 42 baseballs within the game.
- "Groundhog Day" Loop: Eventually the group falls into a pattern of "arrive at library, do quests, challenge Time Eater and lose, and repeat".
- Guide Dang It!: Getting all of the medals and baseballs without realizing that expanding Toyopolis in the Game Gear era also resets it in the Dreamcast era, requiring revisiting it to collect the collectibles in there before expanding it a second time.
- Headbutting Heroes: Most the Sega Hard Girls oppose their Neptunia counterparts because they believe the goddesses are unfit for the role.
- The Hero: IF is this in the game rather than Neptune.
- Hopeless Boss Fight: The first fight against the Time Eater is most likely hopeless on your first playthrough. Unless you grind, it is much more powerful and can make short work of your party.
- It's All About Me: Segami's motivation begins and ends with stopping the CPUs and Sega Hard Girls from fighting. However, due to her status as an Amnesiac Hero, she usually can't come up with a better explanation than "We have them stop from fighting because I say so". Combined with her rather bitchy attitude and refusal to accept any other methods, she comes off a spoiled brat who's upset she doesn't get her way.
- Level-Up at Intimacy 5: For the CPUs to be able to unlock their final Class, they must each reach Lily Rank 5 with IF. Same with the Sega Hard Girls and Segami.
- Level-Up Fill-Up: On the upside, it kicks in for both the character level and the class level. On the downside, it only refills HP, not SP.
- Macrogame: Levels, Class Levels, and Skills are carried over to each new loop. It's also required to fight Delphinus.
- Magic Is Rare, Health Is Cheap: HP restoring items are available from the shop right away. SP restoring items are only found in the field or completing quests that make some of them available in the shop.
- Malicious Misnaming: Nobody likes Bike Neptune or her color scheme, and most characters, especially Segami, derisively call her "Crap bike!" Nepgear's nickname of "Maniacal Mechanic" isn't any more flattering.
- Mass Monster-Slaughter Sidequest: Many of the quests require you to defeat a certain number of enemies to complete them.
- Mood Whiplash: When IF and Segami first escape being devoured by the Time Eater, they both lament the loss of Neptune and Sega Saturn. Then IF realizes that her bike is now a purple color, and the mood suddenly becomes more silly.
- Multiple Endings: There are Bad, Normal, and True endings, and which one you get is determined by when the Time Eater is defeated in the story.
- Nice, Mean, and In-Between: Nepgear is the Nice one since she treats Bike Neptune well due to her being a fan of robots and machines. Segami is the Closest-to-Mean one due to her getting into arguments with IF when Segami's trying to stop the Sega Hard Girls from starting fights. Although, underneath it all, she's not necessarily that bad. IF is the In-between one since she mediates between the two. She's the most laid-back and level-headed character in the game, although she sometimes loses her sanity when she has to deal with Segami.
- Not in the Face!: One of Neptune's possible lines if she's attacked.
- Not Quite Dead: The Normal ending. Somebody should probably have checked to make sure the Time Eater really was dead.
- Not So Above It All: During one attempt to stop Neptune and Segami's fight, IF and Neptune have fun making up a scenario where Neptune turns evil and adopts a villain name.
- Oh, Crap!: Everyone upon realizing that they have to fight Iris Heart. Or just her being present, really. Turns into a
Moment of Awesome for Mega Drive when she, trying to determine if she actually has a problem with Iris Heart or not, ask Plutia to transform when they're in the library. Everyone else freaks out...but Mega Drive just states that she doesn't really have strong feeling towards her, including asking if Iris Heart feels the same (which proves interesting as back in the main timeline she has massive problems toward Iris Heart). This actually makes Iris Heart comment about Mega Drive being a buzzkill and transforms back. - Only Known by Their Nickname: Segami is always called as such. Most of the characters don't even know her real name.
- Peninsula of Power Leveling: Due to the non-linear progression of the game, dungeons with much stronger enemies than expected can open up at almost any time, giving the player a chance to take on much stronger monsters for greater experience early on.
- Power Copying: Segami can transform into any of the playable Sega Hard Girls and use any abilities they have equipped.
- Punny Name: Segami can be seen as a combination of Sega and megami ("goddess"). It also foreshadows her true identity as the creator of the Sega Hard Girls.
- Red Oni, Blue Oni: Segami is the Red to IF's Blue. Segami is more irate and obnoxious while IF is more laid-back and mature. Which is funny, because with Flame Awakening active, their colors are subverted.
- Reset Button: Should the party lose to the Time Eater, Segami rewinds them to before they first arrived at the library.
- Ripple-Effect-Proof Memory: When Segami rewinds time, she, IF and Neptune still remember what happened in the previous loop. This also applies to the party members who end up at the library for one reason or another.
- Running Gag: IF and Segami telling Neptune to either shut up or to stop changing topics.
- A sadder running gag is that in every era there is someone saying they need medicine for a sick family member (except for the Deer Girl who denies she is intending to sell the medicine) and a couple of people saying they can feel someone they love close-by but are sad they will likely never get to meet them.
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- Sacrificial Lion: Neptune and Sega Saturn are devoured by the Time Eater early in the story, showing just how dangerous the situation IF and Segami face is.
- Screw This, I'm Outta Here: Sums up the Bad Ending, as IF does not return to the Library to continue fixing history unlike in the Normal Ending where that becomes an option.
- Set Right What Once Went Wrong: Restoring the world in IF's time requires ending the wars between the CPUs and Sega Hard Girls that lasted for multiple eras.
- Shout-Out:
- One way to acquire items in this game? Hit floating blocks from underneath.
- Unlocking IF's Ninja class has Neptune cheer her on with "Go ninja, go ninja, go!"
- Skill Slot System: Each character has three slots they can use to equip moves or buffs, which can be increased to five by completing the appropriate quests.
- Skippable Boss: Based on whether you side with the Goddess or the Sega Hard Girl in the Dreamcast and Sega Saturn Eras, you can avoid fighting Neptune (as Purple Heart) and Uzume. This does, however, mean that you must instead fight their Sega Hard Girl counterpart twice as you go through the game.note
- Something They Would Never Say: Bike Neptune believes this is why Nepgear is the one possessed by the Time Eater in the Game Gear era. Subverted when she's proven wrong.
- Super Mode:
- IF can invoke a Flame Awakening, which functions similarly to HDD for the other Neptunia characters.
- The party has access to Fever Time, which boosts everyone's stats and prevents the enemy from taking a turn while it's active.
- Teeth-Clenched Teamwork: IF and Segami have very little respect for each other but they work together regardless.
- Tempting Fate: Segami mentions that fighting a Time Eater possessed Plutia would be a nightmare. Guess what happens a moment later?
- Time Crash: Histoire says that history can only repair itself to a certain extent; if too much is lost, it could collapse on itself.
- Time Travel: The game revolves around IF and friends travelling to four different eras in order to Set Right What Once Went Wrong.
- Timed Mission: Played with. There's a countdown for each Quest that will cause the Time Eater to eat that piece of history and power up if the counter reaches 0. However, challenging the Time Eater and losing resets the the timers and restores any quests lost for another shot at completing them.
- Timey-Wimey Ball: The most egregious example is Neptune existing in two places at once: both in her bike form and in her playable humanoid form. Nep-bike even sticks around in multiple endings without any kind of paradox.
- The Unfought:
- Neither Nepgear or Game Gear are ever fought directly.
- Twisted on the True Ending path. By changing the eras before the Dreamcast Era, Uzume and Dreamcast never engage in battle and neither one of them has to be fought while possessed by the Time Eater.
- Tomboy and Girly Girl: IF and Segami, respectively.
- 20 Bear Asses: The usual staple of quests for the series continues as several quests involve collecting X number of monster drops.
- Voluntary Shape Shifter: Segami can transform into any one of the Sega Hard Girls in battle.
