Behind the Scenes of 'Proseka's' 5th Anniversary—The Creators' Challenge of 'Telling Stories with Costumes'

Five years since its launch, Project SEKAI COLORFUL STAGE! feat. Hatsune Miku (hereafter 'Proseka') has evolved beyond a mere music game into a universe that weaves stories alongside its players.

A key element coloring this world is the costumes, which give form to the characters' allure. The unique identity and worldview of each unit are breathed into every detail of the design.

How are the characters' emotions and stories translated into their outfits? What vision has driven the production team's five years of continuous evolution and change? In this feature, we dive behind the scenes of costume production to unravel the core of 'Proseka's' expression from the creators' viewpoint.

The Allure of Proseka and Its Costumes at the 5th Anniversary

Proseka is a rhythm game that fuses Vocaloid culture with smartphone gaming to create a fresh musical experience. New tracks from popular Vocaloid producers debut within the game, while beloved classics are given new life with 2D and 3D music videos performed by the in-game units. Proseka acts as a platform where music is constantly being refreshed.

The narrative is characterized by relatable characters who navigate their personal struggles and grow through music, with the music, music videos, and story all intertwining to deeply portray the characters' emotions. Its polished controls have also earned it high praise purely as a rhythm game.

And you can't talk about Proseka without mentioning its captivating costumes. So, what kind of team is behind the costume creation process?

"Right now, we have a team of three in charge of costume design. We typically assign one person to an event, but depending on the project, all three of us might collaborate on a single event's costumes. Our team structure is flexible and adapts to the situation at hand."

One of the most enjoyable elements of Proseka is "Special Training" (a character progression system that raises a character's level cap, boosts their stats, and unlocks a new illustration). The visual reveal after 'Special Training' is a huge part of the Proseka experience, always generating a massive user response. When these illustrations are unveiled, they're met with a flood of strong reactions on social media, like "This art is divine" or "This really hits home," and they spread like wildfire.

They also become subjects of fan analysis, with players decoding the meanings behind every detailed motif and color choice. This is because the post-training art is seen as a key element that reveals the character's emotions and the event's central theme.

Furthermore, anticipation is high for the 3D costumes created based on these post-training visuals. Players tend to look forward to seeing how these outfits will appear during live performances. The post-training art serves to instantly deepen the character's appeal and the event's theme, acting as a major incentive for players to pull on the gacha.

"In the stories of Proseka, we depict the growth and struggles of the characters. The post-training illustrations express each character's feelings and their current situation, and the event costumes are one way we do that.

We consider various elements like the story, the song, and the character’s emotional state. The costume team discusses what we want to express with the outfits for each event and designs them accordingly."

Designs That Reflect Each Unit's Individuality

A huge part of Proseka's charm is the unique personality and narrative of each of its diverse units.

For each unit, the music, story, and characters are seamlessly integrated, allowing players to empathize with their growth and struggles. This structure, which embraces a wide range of values, is a major part of what makes Proseka so appealing.

"We design the unit costumes to clearly convey the personality and worldview of each group.

For 'Leo/need,' the theme is 'youthful band.' We use shirts and blazers to give them a student-like feel while also incorporating rock elements. The star decorations on their chests and shoulders are a subtle touch that symbolizes the unit."

"For 'MORE MORE JUMP!,' we started with a base of idol-like cuteness and added their trademark three-leaf clover. We created a sense of uniformity while also making sure each character's individual personality shines through."

"For 'Vivid BAD SQUAD,' we centered their look on street fashion. We aimed to create a sense of unity as a group while adjusting the designs to make each character's individuality stand out."

"For 'Wonderlands x Showtime,' we focused on a flamboyance fitting for show performers, while also valuing a colorfulness that can be enjoyed by everyone from children to adults. The result is costumes that are exciting just to look at."

"Nightcord at 25:00 is a unique unit where the members all have different school situations, with their activities centered around an online music circle. To create a student vibe that's distinct from Leo/need, we focused on the theme of 'individualized sailor uniforms.' The key was to express a 'sense of loneliness even while being together'—capturing that feeling of being in the same group but maintaining a distance and a sense of isolation."

"When it comes to event outfits that strongly convey emotions, we are always thinking about how to express the theme and a character's feelings through the shape and motifs of the design. Sometimes, it's hard to create a strong outfit design based on the story alone—like for mixed-unit events where different characters interact, or when an event's key theme is something abstract like 'kindness.' In those cases, we might intentionally use motifs that aren't central to the plot, simply aiming to create a design with more visual impact."

They also mentioned a strong focus on color palettes, styling, and accessories. As each event explores the characters' growth, struggles, and relationships, the range of available motifs naturally expands, allowing for richer expressions.

Sometimes, motifs from previously released outfits are intentionally reused to contrast with past emotions or to emphasize certain elements, showcasing a character's growth. In addition, if members are in conflict within a story, their outfits may be designed to reflect that tension.

It's this meticulous attention to detail—weaving the characters' feelings, growth, and the story's drama into every single outfit—that pulls players deeper into the narrative, fostering a stronger sense of empathy and immersion.

Behind the Scenes of Challenging Outfit Designs

Among all the work over the past five years, the events "Whither This Path of Thorns" and "Back light, Lens Flare" are particularly packed with stories of production difficulties and bold challenges.

"A good example of a challenging production is the outfits from the 'Whither This Path of Thorns' event. The main task was figuring out how to express the emotions of Mizuki Akiyama from Nightcord at 25:00, who felt 'unable to accept reality and wanted to run away.'

We initially felt that 'an outfit covering both eyes would be a perfect fit.' However, we were concerned this might make players feel too anxious, and we hesitated, worried that hiding a character's face wouldn't be well-received.

We gathered opinions from a wide range of people, not just the outfit team, and ultimately decided to make the eye-covering design the main feature, while also providing an accessory that kept one eye visible.

Another bold design challenge was the mouth-covering outfit from 'Back light, Lens Flare.' In *Project SEKAI*, showing the characters' expressions and interactions in the 3D music videos is a huge deal, so outfits that hide the mouth were considered extremely difficult to implement."

"But for this outfit, our goal wasn't just to express emotion. We also wanted it to complement the song and use the mask to give the design more of a punch. We felt it was the right time to take on the challenge of covering the mouth, something we had previously avoided, and this outfit was the result."

An Evolution of Expression Built From the Ground Up

*Project SEKAI*, a massive hit both inside and outside the game, has reached a huge milestone in its fifth year. The 5th Anniversary event, special gachas, and the new song "「pentatonic」" (lyrics and composition by syudou × Balloon) have sparked excitement among long-time fans and newcomers alike.

The "Project SEKAI 5th Anniversary Thanks Festival" held in October was not only a live event but was also live-streamed to cinemas across Japan and overseas, with celebratory messages flooding social media.

This milestone isn't just about looking back; it's about building anticipation for what's next for *Project SEKAI*.

"In the early days, there wasn't a lot of story content and very few existing creative assets, so I get the sense we were still feeling our way through production. As the story progressed, more songs were added and character interactions increased, allowing us to delve deeper into their emotional changes. This gave us more opportunities in our outfit design to ask, 'What should we express this time?'

The core principle of considering what we want to express with each outfit hasn't changed since the beginning. However, as we've gained more production experience, our team's expertise has grown, expanding our range of expression.

We've become better at bringing out the characters' charm through more diverse methods—not just by showcasing the main idea, but also by subtly embedding small motifs or incorporating abstract designs to convey delicate emotions."

The stories, songs, and outfits have all evolved right alongside the characters. The passion and creative ingenuity poured into every detail have resonated with players, creating shared moments of joy and emotion. The world of *Project SEKAI* will only continue to grow, and its characters' charm will be portrayed with even more vibrant detail. The story woven by its community and creators is far from over—it's only just beginning.