How to Throw a Birthday Party for an Oshi Who Isn't There: Venues, Decor and Costs
A “birthday party without the star” (honnin fuzai no tanjobi-kai) is an event where fans celebrate their oshi’s birthday by themselves. You may well have seen the photos on social media: a cake and balloons with an acrylic stand or a plushie at the center.
This article covers everything a first-timer needs to get right: choosing a venue, preparing, decorating and budgeting.
What Is a Birthday Party Without the Star?
It’s a gathering where fans, together or alone, celebrate their oshi’s birthday without the oshi there. It also goes by “seitansai” (birthday celebration), “birthday party,” or “senil party,” the K-pop term.
Celebrating someone who isn’t there may seem odd at first, but the idea at its center is simple: “I want to properly celebrate the day my oshi was born into this world.” It’s a culture of turning a birthday, an anniversary shared by your oshi and you, into a special day with your own hands.
Where to Hold It (Three Staples Plus Home)
| Venue | Rough cost | Good for |
|---|---|---|
| Karaoke room | ¥1,000 to ¥3,000 per person | Anyone who wants an easy start. You can play footage of your oshi while you celebrate |
| Rental space | ¥3,000 to ¥15,000 per room | Going all-out on decorating. Photography-focused |
| Hotel (oshi-katsu plan) | From ¥15,000 per room | A leisurely overnight stay. Plans that allow decorations are increasing |
| Home | From ¥0 | The standard for a solo seitansai. You can keep a saidan (fan altar) set up permanently |
Karaoke room
- Easy to start
- Play footage of your oshi
Rental space
- Room to decorate fully
- Photography-focused
Hotel or home
- [object Object]
- [object Object]
Match the venue to how much decorating and photographing you want to do.
Always check before booking: whether you can bring decorations / rules for sticking things to walls (many venues don’t allow tape marks) / restoring the room when you leave / how open flames (candles) are handled.
Recommended Karaoke Chains (With Oshi-Katsu Support)
The major karaoke chains are now competing on oshi-katsu support, and rooms suited to birthday parties are multiplying fast.
| Chain | Oshi-katsu support |
|---|---|
| Pasela Resorts (in Japanese) | The pioneer of “oshi-kai” (oshi gatherings). Its oshi-kai pack includes an oshi-color drink perk, and it can prepare balloons and cake (including its signature honey toast). The classic choice for birthday parties |
| Big Echo (in Japanese) | “Oshi-color rooms” in 11 colors. The whole room is tinted in your oshi color, so photos look great even with little decorating |
| Karaoke Kan (in Japanese) | Its oshi-katsu rooms, “Kara-Oshi-Kan.” Display shelves and frames in 25 colors let you enjoy building a saidan as is |
Plan details and participating branches change, so check the official site for the latest information before booking.
Recommended Hotels (With Oshi-Katsu Plans)
For a “hocance” (hotel + vacance) style birthday party, a hotel with an oshi-katsu plan is a safe choice. Decorations allowed, a setup for watching video, senil cakes arranged: these plans assume from the start what fans want to do.
| Hotel | Area | Examples of oshi-katsu support |
|---|---|---|
| Hilton Tokyo Odaiba | Odaiba, Tokyo | A balloon decoration plan with a choice of 12 colors |
| Tokyo Dome Hotel | Suidobashi, Tokyo | Oshi-color goods (cushions, lights and more) in a choice of 10 colors. Directly connected to the event venue, Tokyo Dome |
| Sunshine City Prince Hotel | Ikebukuro, Tokyo | Overnight plans in concept rooms. Next to oshi-katsu landmarks such as the Animate Ikebukuro main store |
| Shinjuku Prince Hotel | Shinjuku, Tokyo | Plans with an oshi-color cream soda and a saidan space |
| HOTEL PASELA LIVING | Shinjuku, Tokyo | Large TVs, soundproofing, decorations allowed. Suited to birthday parties that double as watch parties |
| MIMARU | Tokyo, Osaka, Kyoto | Theater rooms and rooms with kitchens. Strong for group gatherings |
Plans change or end depending on the season. Search “hotel name + oshi-katsu” to check the latest plan before booking.
Preparation Checklist
- The oshi items that will be the “stars”: acrylic stands, plushies, trading cards
- A birthday cake (an oshi-color senil cake or a photo-print cake is popular)
- Balloons (oshi color, plus number balloons for their age)
- Background decorations such as garlands and paper fans
- A phone stand and light for photos
- A knife, plates and candles for cutting the cake
- Painter’s tape for decorations (the kind that leaves no marks)
Decorating Tips
1. Narrow your colors to two: “oshi color × white”
This is the single most important point for making decorations look polished at once. Mixing white or gold into oshi-color balloons raises the finish of your photos a lot.
2. Build a triangle of heights
Arrange “tall things behind (balloons, garland), the cake in the middle, oshi items in front” in a triangle, and it looks good from any angle.
3. Use a number balloon for the “that day” feeling
A balloon in the number of your oshi’s age is a staple of birthday party photos. Add just one and you get that special “today is the day” feeling.
Photo-ready tableLooks good from any angle
- Two colorsOshi color plus white or gold
- A triangle of heightsBalloons, then cake, then oshi items
- A number balloonTheir age, for the "that day" feeling
Small choices, big difference in the photos.
More decorating ideas are collected in Oshi Birthday Decoration Ideas.
If you want to build a world for the whole venue, professional balloon decoration is an option. KAZAORI Inc. (in Japanese), the company that runs The Oshi Lab, creates balloon decorations for events and parties matched to your oshi color. Full venue decoration starts in the ¥30,000 range (roughly $200), including setup and removal. Please consult us for occasions on a scale where you want to keep a record of the day, such as an anniversary or a milestone seitansai.
Cost Estimates
First, a rough guide if you decorate yourselves.
| Item | Rough cost |
|---|---|
| Venue (per person) | ¥1,000 to ¥5,000 |
| Cake | ¥3,000 to ¥8,000 |
| Balloons and decorations (DIY) | ¥1,000 to ¥3,000 |
| Total (per person) | About ¥3,000 to ¥10,000 |
With party goods from a 100-yen shop, decorations can look great even at around ¥1,000.
If you hire professionals to decorate the venue, the cost is separate from the above, starting in the ¥30,000 range (depending on the size and setup of the venue). Divided by the number of guests, that’s a few thousand yen more per person, and it makes a real difference to how your photos turn out and how relaxed you are on the day.
- 01Pick a venueKaraoke, rental space, hotel or home
- 02Check the rulesDecorations, tape, candles, checkout
- 03Order the cakeAn oshi-color or photo-print cake
- 04DecorateTwo colors, a triangle, a number balloon
- 05Celebrate and shareKeep guests' faces off social media
Cover the venue, the cake and the balloons, and a first attempt comes together.
Etiquette and Cautions
- Always follow the venue’s rules (decorations, food and drink, leaving time). Fans’ behavior shapes how people see your oshi
- Be careful with official images. Check the rights rules for images used on a print cake
- When posting on social media, avoid showing other guests’ faces or personal information
Summary
A birthday party without the star is something like the culmination of oshi-katsu: making the day your oshi was born special with your own hands. Get the venue, the cake and the balloons right, and even a first attempt will come together.
In the seitansai category we’ll keep publishing articles that make celebrating even more fun, such as decoration ideas and how to build a saidan.
FAQ
Where do fans usually hold a birthday party without the star?
The three staples are karaoke rooms, rental spaces and hotels with oshi-katsu plans. Check ahead of time whether you can bring decorations and what the rules are for restoring the room to its original state.
How much does it cost?
If you decorate yourselves, a rough guide is ¥3,000 to ¥10,000 per person, including venue, decorations and cake. If you hire professionals to decorate the venue, add a separate amount starting in the ¥30,000 range.
Is it okay to do it alone?
Of course. The "solo seitansai," where you set up a saidan at home and prepare a cake, is one of the standard styles, and you can find plenty of examples on social media.
