The "official" fourth game in the Infinity series, composed of Never7, Ever17, and Remember11. However, unlike any of the previous Infinity games, this one has no involvement of either Takumi Nakazawa and Kotaro Uchikoshi, the series' main director and writers.The story is focused on Hayato Hino, a student at Ryusei Academy, where he is a member of the school's Second Science Club. One day, Hayato attempts to test out his "Dragon Unit", a flight pack of sorts, by jumping off the roof of the school. At first, it seems to be going well, until he suddenly sees a girl falling out of the sky. He catches her, and lands to the ground. As soon as she wakes up, she slaps Hayato upon learning his name and runs off.As the days go by as the clubs prepare for the school festival next month, Hayato receives a special chip from a science professor, Genkuro Kanbara, which, when put into his smartphone, might allow him to receive voice messages from the future thanks to it being made from a rare mineral known as the Agastia Stone. After installing the chip, Hayato finds that he is indeed receiving messages, but they're too garbled for him to hear properly. As he tries to figure out the nature of the messages, he has to deal with his own issues as the school festival gets closer and closer...Despite following the idea of routes based around heroines, it is interesting to note that the game is linear, and contains very few choices.
This game provides examples of:
Adaptation Decay/ Adaptation Displacement: invoked Both are discussed in Nanari's Route, who, when hearing of a movie adaptation of a book she read, mentions how the novel was apparently much darker than the movie. As for the latter trope, Hikari express surprise that there was a novel.
Alliterative Name: We have Hayato Hino, Hikari Haruna (Hikari Hino in the future), and Tamaki Tatekawa.
Anguished Declaration of Love: Hikari's Route, where she confesses to Hayato after he finds her at a bridge after looking for her all day, since she assumed he stuck her up on a "date". After thinking it over, Hayato decides to confess as well.
Babies Ever After: Not seen in-game, but guaranteed for Hayato and Hikari several years down the road, what with Akari's existence being ensured. Indeed, at the end of the credits, we see several shots of Hayato and Hikari's future with Akari.
Big Brother Instinct: Yuzu's brother Shitora, though it's played with in that he's her younger brother. His reason for this is because he once got injured badly when going into a haunted house with Yuzu once, where the last thing he saw before he blacked out and the first thing he saw when he woke up was Yuzu crying, so he vowed to never let her cry again.
Big Damn Heroes: In the climax of Arika's Route, when Hayato and Akari are trying to get to Sky Tower in a limited amount of time, the rest of the cast shows up to help them out in different ways.
Big Eater: Takeshi, Hayato's fellow Science Club member, who enjoys eating all the time.
Bittersweet Ending: Akari is sent back to her time, reunites with her parents, and finally makes up with her father after realizing he truly did love her, but the present Hayato and Hikari will have to start the whole process all over again in a few years to ensure the Stable Time Loop continues, deceiving their future daughter for most of her early life.
Broken Pedestal: Hayato briefly goes through this in Nanari's Route when he loses faith in Professor Kanbara for apparently abandoning Nanari for research. He gets over it quickly once he learns of the professor's true motives, though.
Casanova Wannabe: Yoshito, who never really tries to make the moves on anyone, but is always making somewhat lewd comments.
First Name Basis: An important plot-point in Tamaki, Yuzu, and Nanari's routes, where all of them are initially unable to call Hayato by his first name (calling him either "Hino" or "Senpai"). A big shift in their relationship is noted when they finally can call him by his first name.
Future Me Irritates Me: Upon hearing about his future self from Akari, Hayato expresses irritation towards his future self, wondering how he could have turned out that way. It's later subverted, though, when he learns of his future self's true motives.
Get Back to the Future: This is the main goal of Arika's Route: repairing her time machine so she can go back to her time. As it turns out, this is the key to breaking the infinite loop, for with Akari back in her time period, she won't be creating another Temporal Paradox.
Hey, You!: Arika never calls Hayato by his name, usually calling him either "you", or some variation of "stupid scientist". In her route, she eventually settles for calling him "Hayato Hino"and later, "Papa".
I Want My Beloved to Be Happy: In Tamaki's Route, Hikari helps Hayato out and encourages his relationship with Tamaki, even though she loves him.
It's All Junk: In Arika's Route, Arika threatens to burn the parts necessary for her time machine unless Hayato makes a choice between preserving all of his inventions or the parts (essentially telling him to choose between his work or his family). He chooses to preserve the parts.
Jerkass Fašade: Future Hayato deliberately ignored Akari because he needed to finish the time machine in time so that he could send Akari back to the past to ensure her existence. However, he couldn't risk her learning about the plan, so he acted indifferent.
Jetpack: The Dragon Unit that Hayato's making is essentially this, but he's never made on that lasts very long, or has other problems.
Kid from the Future: Arika (real name: Akari), who turns out to be Hayato and Hikari's daughter from 22 years into the future.
Lost In Transmission: All of the voice messages Hayato receives are like this, which is why he can't understand most of them: he can hear part, but not all, of the message. Notably, how garbled each message is depends on the route: In Hikari's Route, he can hear more of it, can barely hear anything in Tamaki and Yuzu's Routes, can hear about half of it in Nanari's Route, and almost all of it in Arika's Route.
This turns out to be directly related to the flow of time: in the worlds where the probability of Akari being conceived is higher (Hikari and Nanari's route, where he doesn't choose between Hikari and Nanari initially in the latter), the audibility of the message is higher because its closer onto being the "right" path that doesn't contradict with the future, while the reverse happens in worlds where the chance is lower (Tamaki and Yuzu).
Luke, I Am Your Father: Nanari is actually Kanbara's daughter, though it's subverted that both of them know this and it's not supposed to be a secret: the only one this comes as a surprise to is Hayato, who was unaware. Her father's reaction is pretty much "Oh, guess I forgot to mention that."
Luke, You Are My Father: Subverted- while this does indeed happen, it's Hayato who figures out that Arika is his daughter beforehand, and all she does is confirm it for him.
Missing Mom: Nanari's mother has been dead for over ten years.
Mysterious Informant: The mysterious sender from the future who keeps sending Hayato voice mails. It turns out the sender is none other than the Future Hayato himself, who is sending messages in order to guide his younger self on the right path by giving him advice.
Parental Neglect: Hayato mentions that both of his parents are overseas for work, and he has no idea when they'll get back. He doesn't seem to mind much, though. As it turns out, they don't exist in this timeline, as they exist somewhere in the far future.
This turns out to be Hikari's main issue: when she was a kid, she used to try out in many different acting and music auditions, but failed each time. At first, her parents were supportive, but as time went on, they eventually started spending more and more time at work to avoid seeing each other, and as a result, their relationship has turned cold and they almost never return home. As a result, Hikari has some severe self-confidence and loneliness issues, as she tries to hide her insecurities behind a cheerful facade.
Arika/Akari also suffers from this, with her father (Hayato) neglecting her and her mother (Hikari) for his work and research, which caused her to hate him. However, this is subverted in the end, where it turns out the reason Hayato was working so hard was to build a time machine in time so that he could send Akari back in time to create the Stable Time Loop that will ensure her existence. In other words, he did it all for her. In addition, Hikari was in on the plan the whole time, and knew he wasn't neglecting them.
The Plan: The whole plot was set up by Future Hayato (with the help of Future Hikari) in order to create a Stable Time Loop in order to ensure Akari's existence.
School Festival: Most of the routes lead up to this, though exactly what Hayato does for the festival depends on the route.
Shipper on Deck: Not exactly a shipper, but in Tamaki and Yuzu's Routes, Arika helps Hayato realize that he has feelings for them, while in Nanari's Route, she tries to set Hikari up with him. This is most likely because she was trying to break up her parents in order to make sure Hikari didn't end up unhappy, but when time kept looping, she decided she needed a different approach
Stable Time Loop: This turns out the be the whole purpose of the plot: in order to make sure that Akari existed in both 2018 and 2040, Future Hayato put everything he had into building a time machine so that he could send her back in order to maintain her existence. This sends her back to 2018, retaining her existence, where Future Hayato sends messages to Present Hayato in order to guide him. Present Hayato sends Akari back to her time, and armed with the knowledge from his future self, begins the process all over again.
Suddenly Voiced: Hayato's voice is only heard twice in the game: once on the audio recording he leaves on his smartphone that Hikari plays once, and his future self through the voice messages, though it's not clear its him until near the end of the game.
Temporal Paradox: Arika is accidentally creating these: by preventing her own conception, her existence is denied, creating a paradox that loops time backwards.
However, this turns out to be false. The true reason for the paradox is that Akari can't travel back to her time by October 13th, which causes the Stable Time Loop to break. As a result, this creates a time paradox that sends time looping back to September 11th, at the moment of Akari's arrival.
Theme Tune Cameo: In her route, Hikari blatantly hums the game's opening song several times. Arika hums it once too, as she learned the song from Hikari, her mother.
This turns out to be a key plot point in the end: in order to activate the time travel function on the Dragon Unit, Akari needs to sing the song (which is the password). Unfortunately, she doesn't remember the full song, but fortunately, Hikari happens to call at that time, and sings the song for Akari, who then remembers the lyrics and sings the rest of it.
Tsundere: Arika. Tamaki not only identifies her as one, but also calls her "Tsunderika" at one point.
Workaholic: Professor Kanbara is this, frequently staying in his office overnight. Hayato also has a few traits of this, as he sometimes neglects others in order to focus on working on machines.
Both of these tendencies come back to bite them in the ass, as it leads to both of them having awkward relationships with their respective daughters, though this is subverted in Hayato's case, as the reason he became a workaholic was to ensure Akari's existence (plus, Hikari was in on the plan).
Yaoi Fangirl: Tamaki, who not only is a fan of yaoi, but apparently has written some yaoi doujinshi herself.