- _1-2 generations prior to the events of the first game:_ A phenomenon envelops Earth in the isekai word; the sky becomes pink and equally luminescent at all times of the day, and people begin arriving from other parallel worlds, often in the general vicinity of the corresponding place they unwittingly left from.

1-2 generations prior to the events of the first game: A phenomenon envelops Earth in the isekai word; the sky becomes pink and equally luminescent at all times of the day, and people begin arriving from other parallel worlds, often in the general vicinity of the corresponding place they unwittingly left from. Some of them eventually get a lucky break: whether days or years after their arrival, a change in their perception of the sky and a general sense of unease can alert them that a “gate” back to their universe is open, and once in the gate’s vicinity they are inescapably drawn back to their universe of origin; people trying to use a gate to a universe other than their own remain in the isekai world, their bodies heavily damaged by the attempt, but this is rare and lethal enough that it doesn’t become common knowledge.
To counteract the myriad semi-mutually-unintelligible parallel languages/language variants problem isekai victims have, some Esperanto speakers propose a specific variant of Esperanto as a universal language to teach new arrivals; they name it ‘Juliamo’, for ‘July love’ (as it was a July when the world became an isekai destination). Its usefulness causes it to catch on to daily life for natives and vizitantoj (‘visitors’, or isekai victims) alike, to the point it starts to supplant some local languages (including the isekai world version of Japanese in its Japan).
The uncontrollable influx of people, the day-cycle changes and the spread of Juliamo eventually fuel a simmering anti-vizitantoj sentiment through local populations. Vizitanto administrations are created to help newcomers acclimate to life in their destination world, beset by this resentment from all angles; in particular, the Japanese one encourages vizitantoj to find “guardians”, natives or naturalized people who take on responsibility for their behavior and well-being.

Mai crosses over as a high-school-age kid. She has trouble finding a guardian for several years, until a local family who had difficulty conceiving decides to take her in.
Mori Reiko crosses over at an unspecified time around Mai’s, as well.
Kanako is born to Mai’s foster family. Feeling unwelcome due to the parents’ focus on the newborn, Mai, who is barely done with compulsory education, decides to move out, naturalize and go live on her own. Presumably hurt, her foster parents decide to remove all traces of her in the house, hiding family photos and raising Kanako without telling her she had a stepsister.
Mai and Reiko meet and fall in love. They move together in what is likely Mai’s apartment. They promise each other that they’ll be together forever, though this version of Japan also doesn’t have weddings between people of the same gender. Throughout this, Mai keeps a diary of her life that she shows Reiko.
Mai visits her former foster family, presumably partly to reconcile. They introduce Kanako to her as a ‘family member’ without telling her the story.
Mai begins seeing the change in the sky that heralds the arrival of her gate. She is torn by the want to remain with Reiko and the burning wish to return home. She tries to compromise by pushing Reiko to come with her. They both find and pass through the gate; Mai leaves, but Reiko, who isn’t a native of that same universe, is severely hurt and is found in a coma, still in the isekai world.
Kanako finds the hidden photo albums of her family rising Mai. She confronts her parents, who admit to hiding the truth. This breaks her trust in them, in herself (feeling responsible, through her birth, for the disharmony between her parents and Mai) and in vizitantoj, whom she projects her anger on.
Reiko wakes several weeks later from the coma. She will stay in the hospital a long time after, and falls into a deep depression. When she is released, she pursues naturalization and a job at the vizitanto administration, taking the name Rei Arbaro. She copes by living in Mei’s apartment and continuining her diary, imagining Mei meeting Rei Arbaro and looking at herself as a new person through her lover’s writing voice.
Rei finds Ruka (age 8) at Sugita station, apparently having crossed over recently, and recognizes the Japanese on her baseball cap as similar to her world’s own (and ours). She brings her to the administration, which gets her into an orphanage. Rei, taken with the kid, pulls some strings so that she can see her regularly. Something traumatic happens to Ruka in the orphanage that the game never makes us privy to, but that seems to drive a rift between Ruka and the administrators there and drives Ruka to become self-sufficient.
Kanako has a significant health scare that keeps her out of school for a year. She enters one grade lower than is usual for her age.
Rei becomes Ruka’s guardian and foster mother. Ruka moves in with Rei and grows up in the apartment with her. She eventually enters school, where she ends up in Kanako’s class.
Kanako and Ruka become friends when Ruka is the only kid to be accepting of her prickly, trauma-driven ways. Ruka hides her vizitanto status from Kanako and everyone.
Ruka pushes for further independence. She emancipates and asks to be living by herself, even passing an exam to be recognized as a guardian — a move that Rei suggests to ensure she will be given a wider berth by the administration. Rei moves out, focusing more on her job as a library clerk in the vizitanto administration, but the two keep a weird but loving rapport even as they live apart; Ruka inherits her apartment.
Kanako discovers that Ruka is a vizitanto when a slip-up becomes the subject of vicious rumors around the school. Her rage is misinterpreted, causing opportunist kids to use it as an excuse to further bully Ruka as “Kanako’s betrayer”. Ruka is given special dispensation to use the library to study with Rei as her tutor three days of the week, to avoid repercussions at school.
Rin, an energetic Japanese girl with undiagnosed ADHD and depression, crosses over from “our” Japan into the isekai world. She is found and taken in by Ruka. EVENTS OF THE FIRST GAME BEGIN HERE.
Rin and Ruka bond quickly under the supervision of Rei. Ruka applies to be Rin’s legal guardian. The two live together at Ruka’s place, Mai’s old apartment. Rin clumsily begins to learn Juliamo, and helps with Ruka’s budding Japanese. Miss Rei schools both kids, pushing Rin to learn Juliamo while also overseeing Ruka’s education.
Rin finds Kanako and other people teasing Ruka on the way back from school. She defends Rin to them, using her shaky Juliamo to rebuff them. Kanako takes this for a wake-up call and realizes, after it, that she’s been an ass.
Rin has a chance encounter with Rei on a weekend, when she sees her in a cafe dressed in mourning garb. Rei, who is very reticent about her own past, tells Rin a story that is just the account of what happened between Mai and her, thinly veiled as “it happened to a friend”.
Rin and Ruka both begin to see a shift in the sky, signaling that their gate is about to open; they confide to Rei but keep it a secret from each other. This strains their relationship, as emotions run high and communication — already hard over the language barrier and Rin’s untamed impulsiveness and RSD — starts breaking down.
ENDING A (BAD)/B (TRUE): Rin is drawn to the gate, and Ruka follows her. The gate begins attracting her inescapably. Rin can either accept Ruka’s hand trying to pull her out, or swat it away to prevent her from falling into the gate (and possibly harmed like she is aware “Rei’s friend” was). In the latter case, she crosses over alone, separated forever from her love. In the former, it turns out Ruka was originally from “our” universe too! They return to “our” Japan together ever after.
ENDING C (MEDIUM): Rin decides to hide at home so that she won’t be tempted to see the gate, which opens and closes. Rin and Ruka are together in the isekai world. In the ending of the first game, Rin becomes bittersweet, and not talking to Ruka about the choice she made drives a subtle wedge between them over time.
SEQUEL BEGINS HERE. Rin has begun Ending C from the first game but hasn’t decided yet whether to tell Ruka or not about what happened. You can make the choice to cement Ending C, or start opening up — slowly, painfully, and still through the language barrier — to reprocess what happened together.
ENDING A (BAD): Ending C from the first game plays again.
ENDING B (MEDIUM): Rin opens up about that hurt but not about her feelings of jealousy and RSD against Kanako; her wilting doesn’t create the space for Ruka, who is used to hold onto her own secrets, to also open up. After a sudden fight that Rin doesn’t understand the origin of during an otherwise nice date, the two split up temporarily, but Ruka cannot stand it and asks Kanako to find Rei. The two resolve to talk and be together even if the past is hurtful for them.
ENDING C (GOOD): Rin opens up about both the gate and her feelings of jealousy after seeing Ruka and Kanako talk together after the bullying. Her butting in causes misunderstandings due to the language barrier, but her earnestness and her request to help from Ruka drive Kanako to open up to Rin about why she is so prickly and angry with her (and reveals her past). Ruka is inspired by her friend opening up to also open up about the gate having also come for her. She and Rin process the hurt together, growing closer — to the point that, some time later after a fun birthday party, Ruka confesses to Rin her secret name, one her mother had asked her to ‘never give to strangers’ because, if she did, ‘she might not return home’: her real name is Alice, and she can reveal it now that she’s sure she wants to be with her forever in the isekai world.
DAYS GONE BY SIDE STORY: Rei, still quiet about her past, is driven to reminisce with Rin, Kanako and finally Ruka about Ruka’s life, but can’t help revealing some things about her own in the process. She gifts Rin the locked room in the apartment — her and Mai’s old bedroom — as her own room, ending a year of Rin sleeping on Ruka’s couch. She gives Kanako the last copy of the Japanese-from-her-world-to-Juliamo dictionary she authored, when Kanako expresses the wish to understand Rin and Ruka’s words more. She reminisces with Ruka about her emancipation and her failings as a traumatized adult and guardian, but Ruka calls her “her mom” — not ‘foster mother’ or ‘guardian’ — for the first time. She finds happiness in being the mother figure of a band of weird gay teens bound together by the weird physics of the isekai world and their growing affection. The end.