Untitled

First off, what is a SEKAI? As stated multiple times in the game, SEKAI are worlds inhabited by Virtual Singers that are created by particularly strong feelings. These feelings can be those of a singular person (e.g: Tsukasa or Mafuyu), or ones shared by many (like the other three units). The only thing that determines whether or not a SEKAI is created is how powerful those feelings are. Additionally, even if they didn't create the SEKAI, other people with similar feelings can in special instances access and influence the SEKAI (refer to WonderlandsxShowtime or 25-ji, Nightcord de.).

SEKAI can be accessed through an untitled audio file that will appear on the owner's or accessor's computer or phone. Once the person has discovered their true feelings that the SEKAI is linked to, the untitled file will become a song. More songs can be created by the SEKAI as new feelings are uncovered, as demonstrated in event After Lives. The main stories also show that the singers will know the lyrics to the song even if they have never heard it before nor know what the lyrics should be before singing.

Despite what some believe that the SEKAI are inside the phone/computer of the accessor, it is shown on multiple instances that the characters retain their phones inside the SEKAI and can still use them, suggesting teleportation. We can also take Rui's observations from the main story into account here, that the SEKAI is a physical location rather than a virtual world. It's all but confirmed that SEKAI exist on a separate dimensional plane. That said, the phone/computer is the key to remaining in the SEKAI. Should the device run out of power, the connection to the SEKAI is severed and the person will be returned to Earth. The other way to exit SEKAI is to manually pause the Untitled song.

(TL by Puroeng on YT)

At the Beginning of SEKAI With You goes in depth on how SEKAI are formed and how they develop. SEKAI are initially formed as a Fragment of Feelings when a person or group of people exhibit a strong, unyielding desire. School SEKAI was formed when Leo/need saw the meteor shower as children and wished to stay together forever (roughly 6-7 years ago), Wonderland SEKAI formed when Tsukasa was a kid and wanted to make Saki smile (roughly 10 years ago), and Empty SEKAI was formed when Mafuyu started to lose sight of herself and wanted to find her true self again (roughly 3 years ago).

Stage and Street SEKAI aren't entirely clear. Stage SEKAI's Fragment was shown to form when Haruka, Airi, and Shizuku initially debuted as idols. However, all of them debuted at wildly different points in time. Haruka debuted earliest, so we can assume the Fragment formed then (an unknown amount of time ago). Street SEKAI's Fragment is actually never shown forming, so the trigger is unknown. All we know is that it formed during or just after RAD WEEKEND, 3 years ago.

SEKAI grow and change over time. This was first mentioned in Miku's Vivid BAD SQUAD 2* story and was since repeatedly mentioned in Colorful Festival card stories. When a SEKAI is in it's Fragment stage, it sometimes may be able to hold a physical form for a short amount of time. This physical form can be accessed through a glowing orb of light (as shown in the gacha animation) and has to be accessed inside of a fully formed SEKAI. Some Fragments are only temporary and will never become a full SEKAI, something that is alluded to in a few ColoFes stories as well.

If the feelings that formed the Fragment continue to stay incredibly strong, they can manifest into a fully-fledged SEKAI. Again, At the Beginning of SEKAI With You goes into more depth about this. For School SEKAI, it formed when the girls were separated from each other in middle school (~2-4 years ago), Stage SEKAI formed when Minori was attending one of her auditions, which was around the same time as when Haruka, Airi, and Shizuku began to feel dissatisfied with their careers (roughly just over 1 year ago), and Empty SEKAI formed around the time of the Someday, From the Depths of Despair event.

Wonderland SEKAI notably became fully formed incredibly quickly, when Tsuaksa was still a child (hence the presentation of the SEKAI and the fact that he doesn't even remember the feelings that created it when he first discovers it). It is unknown when Street SEKAI fully formed, but it seems to have been almost instantaneous, with the newly formed SEKAI being shown in scenes set not too long after RW. The vagueness could mean that it's possible that this will be elaborated on later.

(TL by Puroeng on YT)

It's not quite clear as to whether you can always access a SEKAI as soon as it has a physical form. In the main stories, the characters first discover Untitled on their phones when it flashes in response to them experiencing the feelings that led to the SEKAI's creation (e.g: Ichika wanting to mend her friendship with her childhood friends). The characters have no prior knowledge of Untitled being on their phones or computers at this point. Beginning of SEKAI somewhat contradicts this, by having Miku and KAITO constantly trying to reach out to Tsukasa and have him find untitled throughout the past 10 years. However, you could possibly say that the file wasn't there until he was 17 to justify why he didn't find SEKAI and respond to Miku and KAITO earlier.

SEKAI also continue to grow even after they obtain a permanent physical form, something which was first hinted at in Miku's Vivid BAD SQUAD 2* story, and later became the focus of the World Link events. As the feelings that created them continue to grow and change, the SEKAI continues to grow with them. It should also be noted that SEKAI, according to Miku's Protective Gaze 3* story, will never disappear, even if the creator were to forget about it.

The final thing to cover here is the Tree of Feelings SEKAI. Last year I wrote a post speculating on some of the lore surrounding this SEKAI, most of which was confirmed to be correct as of Beginning of SEKAI. That post covers this final part in mroe detail, so read that if you're interested. The Tree of Feelings SEKAI is a mysterious Fragment SEKAI that so far has appeared in Miku's Where Feelings Come Together 4* story, and the events Sakura Across SEKAI, Interconnecting Our Feelings and Let Your Song Resonate Throughout SEKAI. The Fragment briefly obtains a physical form whenever the inhabitants (human or Virtual Singer) of all 5 main SEKAI are experiencing a shared feeling.

As mentioned by MEIKO in Sakura Across SEKAI, the Tree SEKAI appears to be some sort of Nexus between the 5 we follow in the story. This is later confirmed to be the case in Beginning of SEKAI, with the same tree appearing in all 5 SEKAI, occasionally transmitting music from the other SEKAI it is connected to. Stage SEKAI MEIKO also mentions in the Sakura Across SEKAI story that this has never happened before.

While animated by an outsider source, so not entirely reliable, the NEO MV suggests that the Tree SEKAI is beginning to take on a permanent physical form with its own Untitled song. The Untitled song in this case is, of course, NEO.

Part two: What are the Virtual Singers? The Virtual Singers in each SEKAI are stated in chapter 10 of the WonderlandsxShowtime main story to have physical bodies. While we don't really know anything about their biological make up, they're at the very least, humanoid and sentient instead of being holograms, though they can present themselves on Earth in that form through any device that can display holograms (or on computer screens as seen in a few 25-ji, Nightcord de. stories and cards). While implied in Miku's Protective Gaze 3*, it is confirmed by Beginning of SEKAI that the Virtual Singers are immortal and don't physically age.

Versions of the Crypton VOCALOID characters that resemble their real-life character designs exist "between the SEKAI", which appears in-game to be some sort of white space, however the I'm Mine another cuts may be set in this location. While very early stories don't make it entirely clear, it is officially confirmed as of Sakura Across SEKAI that the Virtual Singers in each SEKAI are completely individual entities, rather than the primary Virtual Singers travelling between SEKAI and changing their form.

The versions of the Virtual Singers in each SEKAI are aware that they are derivatives of their primary form (mentioned in both Virtual Singer events). The derivatives are influenced by the owner(s) of the SEKAI, taking certain aspects of their psyche and abilities. It should also be noted that not all SEKAI start with all six of the Virtual Singers. This is heavily implied to be the case with Street SEKAI and Stage SEKAI, but it not the case with the School, Wonderland, or Empty SEKAI. School SEKAI started with just Miku and Luka, with the other 4 arriving during event stories. Wonderland SEKAI started with Miku and KAITO, though the Kagamines arrived immediately following the main story, shortly followed by MEIKO and Luka. Empty SEKAI started with only Miku, with the other 5 vsingers appearing in response to changes in Mafuyu and the others' mental states.

It is explicitly stated in Len's Vivid BAD SQUAD 2* card story that the Virtual Singers possess supernatural or magical abilities, and are actually incredibly similar to humans, although they have the innate ability to help people discover their true feelings. Despite this claim, Wonderland SEKAI MEIKO is shown to have superhuman strength, Wonderland SEKAI Luka's sleep schedule is controlled by Tsukasa and the others' emotions, and Wonderland SEKAI Miku is ambiguously a cat-humaoid hybrid. Not to mention the sentient plushies, and singing flowers and actual Phoenix. However, these can be somewhat justified given that the Wonderland SEKAI was largely influenced by the imagination of a 7-year-old child. It was also Street SEKAI Len that made this claim, and that is by far the most grounded in reality of all 5 SEKAI.

Now the final part, building off what Len said about SEKAI not being magical or supernatural. The only justifiable explanation is that they are alternate dimensions, as I mentioned briefly earlier on, where these sorts of inexplicable "magical" things are natural occurences.

So what are some of the physical capabilities of the SEKAI? Let's start with one that applies to all five, the innate abilities to create clothes out of thin air. The unit outfits for Leo/need, MORE MORE JUMP!, and 25-ji, Nightcord de. were all created by the SEKAI, which is mentioned in Honami's Unchanging Flavor 3* card story. The same card story also confirms that these costumes cannot be taken out of the SEKAI. Both Journey to Bloom -HOPE- and a 3rd Colorful Live 4koma illustrate how the costumes form. The 4koma shows it to be instantaneous, much like it is shown in vlives, so it's likely that Journey to Bloom animates the effect to be more visually appealing.

A notable new one is the ability to physically alter a person's appearance. This seems exclusive to the new Fragment SEKAI seen in Kanade and Rui's Bloom Festival 4* card stories, but given that they're technically still SEKAI, this may apply to regular SEKAI as well. In the aforementioned card stories, Kanade and Rui both turn into their younger selves temporarily. Also shown in those two stories and in Airi's To You Who Wants to be An Idol 4* story, the SEKAI (or Fragement SEKAI specifically again) have the ability to temporarily manifest a person's younger self, or separate versions of their present day self. It's shown that this is not a vision but a physical form, although they are clearly presented to have a separate consciousness to the true version of the person. The same can be inferred for the woman who appears in Haruka's Someday, I'll Deliver 4* card story, and Nagi's appearance in BREAK DOWN THE WALL.

A few SEKAI also deviate from Earth's rules of physics, notably, School SEKAI and Wonderland SEKAI. Wonderland SEKAI is incredibly obvious in its deviations, but School SEKAI recently acquired a flying train.

SEKAI also seems to prevent its inhabitants from dying or getting hurt. While falling from the flying train is treated as a danger in the Wonderland SEKAI Virtual Singer main story, Tsukasa falls from a height in Aye-Aye, Let's Aim for the Star that should have killed him, even with safety mats laid out. Wonderland SEKAI KAITO may or may not have been stabbed in the past too, though he is immortal anyway.

SEKAI can also give people amnesia, as shown in Akito's Wanderer's Thirst 4* card story. Additionally, whenever the unit representatives are summonned to sing together in Virtual Lives, or when they visit the Tree of Feelings SEKAI, their memories are wiped afterwards. However, unlike Akito's case, it's Miku herself who erases the unit reps' memories.

Lastly, the audiences in Virtual Lives. Obviously, no one inhabits the SEKAI other than the owner(s) and the Virtual Singers, so who makes up the audience. As explained in the First Star After the Rain After Live, these are Sparks of Feelings. Small sparkling lights (suggested in multiple Virtual Lives to be the small triangles seen floating around in the SEKAI) that respond to the songs heard in SEKAI. These are stated to be the feelings of other people (the player character) that resonate with the music and feelings of the performers.