How to Throw a Birthday Party for an Oshi Who Isn't There: Venues, Decor and Costs

On your favorite performer’s birthday, you prepare a cake or small objects in a color you associate with them. The person need not be there: fans may gather with friends or enjoy a quiet celebration at home. In Japan, this is called a “birthday party without the person present.”

Elaborate decorations and a single cake are both options. Using official venue photographs, this article explains choosing a location, preparing and separating the costs. It also offers facility operators a way to consider what guests need to know before booking.

What Is a Birthday Party Without the Star?

It is a celebration organized by fans without inviting the person whose birthday they are marking. Names include seitansai, birthday party and saengil party. The participants and organizers differ from an official birthday event at which the performer appears.

Friends might talk about favorite scenes, arrange acrylic stands and plushies, or take photographs beside a cake. There is no required group size, scale of decoration or amount to spend. When celebrating someone who has not disclosed their age, or a fictional character with an established profile, work from official information about that person or work.

Choose a Venue by What You Want to Do and What It Allows

Start by deciding whom you want to celebrate with and what you want to do. Talk over tea, watch on a large screen, or arrange goods for photographs? Your purpose helps narrow down the space and equipment you need.

A package called an oshi-katsu plan does not automatically permit sticking things to walls, bringing an outside cake or inviting an unlimited number of friends. Tell the venue specifically what you want to do and confirm permission and additional charges.

1. 01Choose the activityTalking, watching or photographing goods
2. 02Check the spaceSeats, tables and the equipment you need
3. 03Confirm permissionVisitors, outside food, decorations and sound
4. 04Calculate the totalInclude setup, cleanup and optional charges

A package name alone does not establish what is permitted.

Official Photos: Choosing Colors for the Food and Room

Pasela’s Oshi-Kai Afternoon Tea Set

Pasela’s official oshi-kai page introduces an afternoon tea set with eleven color choices. The plan combines a themed-color drink, a small honey toast and afternoon tea.

The image shows differently colored drinks and sweets arranged on tea stands of the same shape. Matching food colors to the goods you bring offers an alternative to building an entire backdrop yourself. The eleven colors are options for the set, not eleven different room types.

The official table lists a three-hour rate per adult of ¥4,480 including tax from Monday to Friday and ¥5,480 on weekends and public holidays. The price includes unlimited soft drinks, sweets and the room charge. These figures were checked on November 1, 2026; reconfirm the store, date and package conditions for your booking.

For four people using the weekday three-hour plan, the calculation at the listed rate is ¥4,480 × 4 = ¥17,920. Account separately for any extra food, drink-package changes or decorations ordered. Since sweets are already included, you do not need to decide in advance that a separate whole cake is essential too.

Look at the Screens and How the Table Can Be Used

The same official page shows example rooms, including room 601R at the Shinjuku main branch.

The photograph shows the relationship between the display surfaces and the table where food and goods can be placed. Consider more than screen size: how many people will sit there, how much space remains after putting down a cake, and where the photographer will stand. This helps you picture how the room will work on the day.

Check video equipment separately from the terms of the work or streaming service. The presence of cables and playback equipment does not establish that any video may be screened. Before booking, check compatibility with your device or discs and whether your intended use fits the relevant conditions.

At a Hotel, Separate Staying Overnight From Gathering Together

A hotel may suit people who want time to decorate or stay until the following morning. An ordinary guest room and a package designed for parties can allow different activities, however. Check occupancy, non-staying visitors, sound levels, outside food and decorations on walls or ceilings.

As an example of where to check equipment, MIMARU’s official FAQ lists possible loan items such as rice cookers, toasters and extra dishes, while explaining that availability varies by hotel. A room described as having a kitchen does not establish that every plate or tool you need for a cake will be provided; ask the property where you will stay.

Even if you want to photograph a particular part of the room, moving hotel furniture is a separate matter. Work within the permitted methods, such as decorations that do not require furniture to be moved or small items that stand without being attached to the wall. Also distinguish photographs of completed collaboration packages from rooms that can currently be booked.

Separate What to Buy From What You Can Borrow

• The goods you want to feature, their bases and protective cases
• Cake or sweets, plates, forks and serving utensils
• The decorations you need and permitted ways of placing or fixing them
• Phone, charger and an optional photography stand
• Participant numbers, booking details and venue contact information
• Time allocated to setup, photographs, eating and cleanup
• Rubbish and carrying bags that fit the venue’s checkout rules

For a cake, confirm permission to bring it, pickup time, refrigeration and allergen information. Candles included with a cake do not automatically mean flames are allowed in the room. You can leave them unlit or use small lights where those are permitted.

Tape requires the same care. Labels such as removable or masking do not guarantee that a product will leave the venue’s walls or furniture undamaged. Check the fixing methods the facility permits and do not attach decorations without permission.

Plan Decorations Around the Photograph You Want

Choose the Colors

One approach is to begin with a small number of colors, such as your oshi color and white. Place the goods and cake you want to use first, then add only the backdrop elements you need. This can also narrow your shopping list. If several colors matter to you, you can use those instead.

Test the View From the Front

Tall decorations at the back, a cake in the center and small goods in front are one possible arrangement. Take a test photograph to check whether faces or names are obscured and whether food is touching merchandise. It will not necessarily look the same from every angle, so choose a direction for the photograph and adjust accordingly.

Match Numbers and Names to What You Are Celebrating

Number balloons can represent a date or anniversary as well as an age. A celebration without an age can still use names, colors and favorite motifs in a commemorative photograph. Increasing the amount of decoration is only one possible way to celebrate.

If inflating balloons yourself, one option is to search Amazon Japan for a balloon hand pump. Check the product description for compatibility with the balloon material and valve, and whether it is for air inflation. Our birthday decoration ideas offer more specific arrangements.

Calculate the Whole Party’s Cost Before Dividing by Participants

Adding a room charge, one cake and a set of decorations to per-person rates can obscure the total. First calculate what the whole gathering needs, then divide it between the people participating.

The following is a hypothetical four-person calculation, not a market average or an actual quote.

Actual costs depend on whether food is included and whether cleaning, overtime, outside-item or cancellation fees apply. Discuss what happens if fewer people attend, how advance payments will be settled, and who takes decorations and goods home. Agreeing these details beforehand can reduce misunderstandings.

¥22,000

Whole-party total in the example

4 people

Assumed participants

¥5,500

Equal share per person

This calculation is not a quote or a measure of typical spending. Actual booking and cancellation conditions apply.

For balloon decoration across a venue, you can also contact KAZAORI Inc., which operates The Oshi Lab. The venue, size, area to decorate, and setup and removal conditions form the basis for discussing the work and price.

Finish With Cleanup After Taking the Photographs

When using official photographs or illustrations on cakes or panels, check the rights holder’s guidance, usage conditions and the supplier’s acceptance criteria. Before posting party photographs, check for participants’ faces, account names or booking information. Ask anyone pictured what they agree to have made public.

Finish collecting goods, removing decorations, dealing with rubbish and checking for forgotten items before checkout time. Build cleanup into the reservation rather than planning to take photographs until the last minute.

Notes From The Oshi Lab: What the Venue Provides and What Fans Create

An official oshi-kai set can reduce the preparation needed by combining a room, food and color choices. Participants still have the pleasure of arranging their own goods and deciding which scene to photograph.

Facilities do not need to decorate every available space. They can explain what is supplied, what may be brought in, and how much time is available for setup and removal, while leaving room for fans to add something themselves. Participants can decide whether to celebrate alone or with friends, and how much to buy, while enjoying the day they want to mark.