Welcome to planDisney!
Haukuna matata! You're not the first person to do this.
If you would like to change your friend's name on his
Disneyland ticket, you have to call the
Tickets services phone line and speak to a Cast Member. They're able to change/update the name on his ticket. Unfortunately, this isn't something that you can do yourself through your My Disneyland account. There also might be a bit of a wait on the phone. If you're calling from Japan, this probably isn't a cost-effective option.
So here's a cheaper option: leave the name as it is. For most theme park tickets, the name on the ticket isn't important. It's more to help you know which ticket is assigned to which person. The important thing is for the person who first uses the ticket to remain the same throughout your visit. Here's what happens: When you enter your first theme park, a Cast Member will take a photo of each person when they first use their ticket. After that, whenever you enter a theme park, they'll use the photo to ensure it's the same person using it. So when it comes to rectifying your mistake it's really up to you. You can call and change it, or just leave it as it is. Either way, your friend won't have a problem entering the theme parks.
There's so much to enjoy and experience during your visit! Make sure you visit
Star Wars: Galaxy's Edge. Your services are required in
Star Wars: Rise of the Resistance. Since wait times for this attraction can get long, I'd suggest arriving at Batuu as close to park opening as possible. You could also purchase an
Individual Lightning Lane entrance if you wanted lightspeed access to this ride. You'll then want to go for an adventure on
Millennium Falcon: Smuggler's Run. This interactive ride will allow you and your friend to test your skills as a pilot, engineer, or gunner. As you trek through Batuu, don't allow hunger pains to turn you to the Dark Side. A delicious trip to
Ronto Roasters or
Docking Bay 7 Food and Cargo will help keep the Force strong. If you'd like to quench your thirst, then a visit to the
Milk Stand for some of that famous blue milk wouldn't be a bad idea either. Finally, keep an eye out for famous characters! You might even see Ahsoka walking around.
Have a great trip! See ya real soon.
Mike