First off, please check out the Japan Embassy website for official info.
Everyone in Japan actually “gets married” in their local city/municipal hall. After doing the appropriate paperwork, the couple has 2 witnesses sign the appropriate paperwork and takes it to their town’s city hall to have it registered. There’s no ring exchange or speeches, just a signing of paperwork. You’re officially man and wife after this, so any sort of ceremony is optional. To me, this seems like a great way to do things: no need to find an ordained person to marry you (or force someone you know to get ordained online). You could go low-key and simply go out to eat or design the crazy wedding of your dreams. Usually the actual day you apply at city hall and your ceremony don’t coincide, leaving the couple to determine what day to actually celebrate their anniversary.
In a chiefly Buddhist Japan, the 2 most popular wedding options are a Shinto shrine ceremony or a Christian church wedding.
The Christian wedding was picked up from the West. There are churches dotted across Japan that are only wedding venues, not actual places of worship. Japan picked up the Western traditions and adopted them to make their own: big white dresses, ring ceremonies, priests, hymns and organ music… Just because you aren’t Christian doesn't mean you can’t have a wedding like one! Receptions too look very Western: everyone gathered for a meal with speeches and various activities. The wedding venue is essentially your wedding planner: they rent the outfits, the venue, make the food, decorate, and help plan the events. Many Japanese couples opt for a Western style cake cutting. Another popular activity is for the couple to light the candles on the guest tables and their own.
The shrine ceremony is traditional Japanese style. The clothes include kimono, robes, and a heavy wig and hood for the bride. Shrine priests wave a bamboo branch, chant, and cleansing and blessing the couple. The pair read a Japanese version of vows together from a piece of paper. It isn't quite the same as vows; it is more of a proclamation of marriage. Another popular tradition includes the couple and their family sharing sips of sake to seal their families together. Western traditions sneak in here also: you can opt for a ring exchange. The shrine could be an actual sacred place of worship, or it could be a shrine set up in a hotel. The Shinto ceremonies tend to be much more conservative and traditional, and often small in terms of guests compared to the Western style.
The first thing a newly engaged couple needs to do (besides revel in their happiness of course!) is determine a time and place. After determining a time frame, finding a place is a bit more of a challenge. Wedding companies usually offer both Shinto ceremonies and Western weddings, so choosing a place based on the atmosphere you like is best. These companies have their own venues with photographers, cooks, stylists, coordinators. They even have their own boutiques full of dresses for you to rent for the day. When you choose a certain place to have your ceremony, you choose to make a wedding plan with them. You can’t bring in your own vendors, but you pick and choose what services you’d like with the company. This doesn’t leave much room for the do-it-yourself types and the ingenuous, but that’s why choosing the venue and company that will work toward your vision is important. My husband and I both wore our own clothes for the reception instead of renting the elaborate costumes, and we also organized and made our own gifts for guests and invitations. Adding many services means the expenses can add up. Japanese weddings are expensive affairs. In my opinion, there really isn’t a cheap wedding in Japan, except for choosing to forego a ceremony. Some of the cost is offset by the gifts of money from the guests (presents are very rarely given). Some Japanese avoid the expensive and time consuming process and go to Hawaii to marry/honeymoon on a beach, since the expenses are about the same.
Here's some basic info if you're interested in learning more: