History Film / TheDoorIntoSummer

* Applied Phlebotinum: Soichiro's Plasma Battery, a semi-perpetual energy source that would revolutionize the service robot industry by making it possible to power androids such as PETE-13, as well as Professor Toi's time machine.

* BlandNameProduct: PETE-13 shows Soichiro video about the disgraced Professor Toi on Wootube.

Soichiro Takahura has had a life filled with tragedy. His mother died soon after he was born, followed by his father when he was seventeen. He was then taken in by his father's colleague, robotics expert Dr. Koichi Matsushita, only for him and his wife to die in a plane crash a few year later. Soichiro is left almost completely alone in the world, except for his pet cat Pete, and Dr. Matsushita's young daughter Riko, who goes to live with her uncle Kazuto.

The story opens in 1995, where Soichiro has followed in the footsteps of his father and Dr. Matsushita to become a talented robotics engineer, as well as a major shareholder in the robotics company founded by his mentor and managed by Kazuto. He remains oblivious to the affections of the now-teenage Riko, in favor of his gorgeous fiance and company secretary Rin Shiraishi.

Rin convinces Soichiro to sign over a significant share of the company, only to later conspire with her lover Kazuto to seize control of the company and sell it to the conglomerate Mannix Corporation, kicking Soichiro out from his own company, depriving him of his research materials and robot prototype, leaving him with a handful of non-controlling shares.

** Kazuto Matsushita = Miles Gentry

* DrowningMySorrows: Soichiro gets heavily drunk after finding out that his fiancee Rin was actually Kazuto's lover and conspired to wrest control of FWE from him. This causes Credeus to postpone his original cold sleep appointment, although Rin arranges for a Mannix subsidiary to freeze him anyway.

** Kazuto is seen giving himself an insulin injection, because he has diabetes. Later Rin gets the advantage of Soichiro by jabbing him in the neck with one of Kazuto's insulin syringes.

** Riko (eventually) by the Satos, keeping her safe from the machinations of her uncle Kazuto and lover Rin.

* ImpairmentShot: A shot from Soichiro's POV as his vision blurs, after Rin jabs him in the neck with one of Kazuto's insulin shots.

* LadyDrunk: Soichiro finds Rin in 2025, living in a filthy apartment, with empty beer cans scattered around, popping pills, and very, very fat. Rin angrily shouts at him that Kazuto died and Mannix folded and she went to jail for cooking Mannix's books.

** Riko Matsushita was presumed dead in the explosion that destroyed the Matsushita family home and Soichiro's private workshop, while in 2025 Soichiro learns that a Riko ''Sato'' had went on to develop the second-generation PETE-2, based on Soichiro's own PETE-1 patent. In 1995, Soichiro sets fire to his old workshop and arranges for the Satos to adopt Riko, keeping her safe from the scheming Kazuto and Rin while ensuring she will eventually become a talented engineer in her own right.
** Kazuto and Rin order Soichiro's research materials and A-1 prototype robot to be confiscated, but the FWE truck carrying them disappears afterwards. Upon returning to 1995, PETE-13 hijacks the truck and takes it to the Sato residence, with the recovered materials eventually becoming the seed intellectual property for Guardian Manufacturing.
** Pete the cat disappears during Soichiro's confrontation with Rin at Kazuto's mansion. When Soichiro later returns to 1995, he picks Pete up through a window and slips away.

* PragmaticAdaptation: Even when the book was published and tolerance levels were much higher for this sort of thing, there were people who expressed discomfort over the central plot of a 30-year-old man more or less falling in love with a 12-year-old girl. In the novel, they joke about getting married when she is ''six''. At the end, Daniel tells 12-year-old Ricky to go into cold sleep and promises to marry her when she's older. This film softens that squickiness quite a bit. The age gap is closed from 18 years to ten and more importantly Riko is aged up to 17. Unlike the book where they joke about getting married, in this movie Soichiro is ObliviousToLove. And at the end, there is no exchange about Riko going into cold sleep or the two of them getting married; Soichiro is quite surprised to find out that Riko waited ten years and then went into cold sleep herself so they would be the same age.

* AnguishedDeclarationOfLove: A crying Riko confesses her long-held feelings to a despondent Soichiro. However, he rejects her due to their significant age difference and the reeling aftermath of Rin's betrayal, opting to go into cold sleep instead.

* DrowningMySorrows: Soichiro gets heavily drunk after finding out that his fiancee Rin was actually Kazuto's lover and conspired to wrest control of FWE from him. This causes Credeus to postpone his original cold-sleep appointment, although Rin arranges for a Mannix subsidiary to freeze him anyway.

* TheSlowPath: Having travelled back to 1995 to help Soichiro, PETE-13 opts to enter sleep mode for thirty years so that he can reunite with Soichiro when the latter takes his second cold-sleep to 2025.

* UncannyValley: Most of the androids in 2025, including PETE-13, the cold-sleep clinic nurses and the Guardian Manufacturing receptionists behave in a stiff, unnatural manner. Gradually subverted by PETE-13, who even learns to give Soichiro an geniuinely warm smile.

* AnguishedDeclarationOfLove: "I've always loved you!", says a crying Riko after the truth about Rin is revealed. He rejects her, because he's emotionally rattled and also because she's 17, instead resolving to go into cold sleep.

* AscendedFanboy: A young Gota Tsuboi in 1995 is inspired by a news broadcast celebrating Soichiro's development of the A-1 robot prototype (along with a time-travelling Soichiro autographing his science textbook) to eventually become the President of Guardian Manufacturing, a key player in the service android industry.

** A TV commercial seen during the opening scenes advertises "cold sleep", the opportunity to go into cryonic freeze and wake up years or decades into the future. This is what happens to Soichiro later in the movie.

* {{Fauxshadow}}: One of the fake news bulletins in the early portion of the movie shows scientists announcing that they've invented teleportation. This is never mentioned again and has nothing to do with the story. (Except that those scientists were probably actually starting to invent time travel.)
* {{Foreshadowing}}:

** While investigating how Guardian Manufacturing bought out FWE using shares intended for Riko, Soichiro learns that the shares were transferred to business tycoon Taro Sato, the founder of Aladdin Industries and an early shareholder in Guardian Manufacturing; furthermore, Sato is listed as Soichiro's patent attorney for the PETE-1 and the Plasma Battery patents. In 1995, Soichiro meets the lawyer Sato, who has been briefed by PETE-13 and provides Soichiro with room, board and resources to complete the design work for the two technologies.

* AdaptationDistillation:
** Daniel's months-long adjustment to life and engineering technology in 2000 are dropped in favor of Soichiro spending a few days to investigate the fate of Riko and the FWE shares intended for her.
** In the novel, Daniel spent some time convincing the Suttons to help him after returning to 1970; when Soichiro awakens from his time jump back to 1995, Sato tells him that PETE-13 had already explained everything to him, the gold has been cashed out and the rest of their plan is underway.

* AdaptationPersonalityChange: The novel's Dr. Twitchell is a bitter drunk who needs to be goaded into sending Daniel back in time, whereas the film's Professor Toi immediately and enthusiastically helps Soichiro. Justified in that Soichiro would return to the past to provide Toi's disgraced past self with the funding needed to eventually complete the time machine, as well as inventing the Plasma Battery to power it.

** In the novel, Daniel spent some time convincing the Suttons to help him after returning to 1970; when Soichiro awakens from his time jump back to 1995, Sato tells him that PETE-13 had already explained everything and recruited him into their plan.
** Similarly, Daniel has to track down and butter up Dr. Twitchell in order to eventually goad the latter to send the former back in time, whereas when Soichiro first meets Professor Toi i 2025, the good doctor eagerly ushers the inventor to his time machine.

** Similarly, Daniel has to track down and butter up Dr. Twitchell in order to eventually goad the latter to send the former back in time, whereas when Soichiro first meets Professor Toi, the good doctor quickly ushers the inventor to his time machine.

* AdaptationPersonalityChange: The novel's Dr. Twitchell is a bitter drunk who needs to be goaded into sending Daniel back in time, whereas the film's Professor Toi immediately and enthusiastically helps Soichiro. Justified in that Soichiro would return to the past to provide Toi's disgraced past-self with the funding needed to eventually complete the time machine, as well as inventing the Plasma Battery to power it.

* WorthlessYellowRocks: PETE-13 explains to a bewildered Soichiro that gold (along with nearly all precious metals) are practically worthless in 2025, having been replaced by digital currency. Professor Toi later provides Soichiro with dozens of gold billions to take back to 1995, where it could be used to fund a younger Toi's time travel research and pay for patent attorney Sato's services.

* WorthlessYellowRocks: For some reason, gold isn't very valuable in 2025. Professor Toi gives him a whole bunch to take back to 1995 with him.

* DramaticDrop: PETE-13, who is supposed to stay behind in 2025, dramatically drops the music player he's holding, and jumps up onto the time travel platform with Soichiro. They go back to 1995 together.
* DrowningMySorrows: Soichiro gets good and drunk after finding out that Rin never loved him and actually is Kazuto's lover and schemed to force him out of the company. This is why he's rejected for cold sleep, although Rin later uses the authorization form to put him in cold sleep anyway.

* LineOfSightName: Sato names his company, the one he's going to found using Soichiro's inventions, "Aladdin" after a poster of Aladdin's lamp on the wall.

* ObliviousToLove: Soichiro has no idea that Riko is in love with him. The presence of his smoking hot girlfriend Rin may be part of the reason.

* RidiculouslyHumanRobots: The PETE-13 robots that exist in 2015 are indistinguishable from humans, except for a certain [[invoked]]UncannyValley manner, and times when they show off their digital irises.
* SecretKeeper: Unlike the Suttons of the original novel (who merely follow along with Daniel's plans with bemusement), the Satos are fully aware that Soichiro and PETE-13 are time travellers, and have all the information needed to actively assist them in their plan.

** While Soichiro originally booked his cryo-sleep with Credeus, Rin instead arranges for Soichiro to be frozen by a Mannix subsidiary instead. After implementing his plans in 1995, Soichiro makes it to his original appointment at Credeus to return to 2025.

** Riko Matsushita was presumed dead in the explosion that destroyed the Matsushita family home and Soichiro's private workshop, while Soichiro learns that a Riko ''Sato'' went on to develop the second-generation PETE-2 robot based on Soichiro's own PETE-1 patent. In 1995, Soichiro sets fire to his old workshop and arranges for the Satos to adopt Riko, keeping her safe from the scheming Kazuto and Rin while ensuring she will eventually become a talented engineer in her own right.

** An embittered and drunk Rin rants that she never received her FWE shares and was jailed for tax evasion, leading to the downfall of Mannix. Back in 1995, Soichiro asks Sato to probe into Mannix's finances.

** Kazuto and Rin order Soichiro's research materials and A-1 prototype robot to be confiscated, but the FWE truck carrying them disappears afterwards. Upon returning to 1995, PETE-13 hijacks the truck and takes it to the Sato residence, with the recovered materials becoming the core IP of Aladdin's future business.

** Riko Matsushita was presumed dead in the explosion that destroyed the Matsushita family home and Soichiro's private workshop, while Soichiro learns that a Riko 'Sato' went on to develop the second-generation PETE-2 robot based on Soichiro's own PETE-1 patent. In 1995, Soichiro sets fire to his old workshop and arranges for the Satos to adopt Riko, keeping her safe from the scheming Kazuto and Rin while ensuring she will eventually become a talented engineer in her own right.

** Riko Matsushita was presumed dead in the explosion that destroyed the Matsushita family home and Soichiro's private workshop, while Soichiro learns that a Riko *Sato* went on to develop the second-generation PETE-2 robot based on Soichiro's own PETE-1 patent. In 1995, Soichiro sets fire to his old workshop and arranges for the Satos to adopt Riko, keeping her safe from the scheming Kazuto and Rin while ensuring she will eventually become a talented engineer in her own right.