Can one person occupy two seats?

I'd like to go to Japan and I've looked at ticket prices. The premium economy is more than double what the economy seat is. Can I buy two economy seats and fly by myself? What would you do to put the name(s) of the passengers and what would happen at the check-in counter. Do international flights have standby-passengers? Would my other seat be taken? I'm confused? I would like more legroom and I can save over $200 if I was to buy 2 tickets instead of one. Thanks.

I don't think that is how it works, but the place to ask is to the airline's customer service, not a Japan travel forum.

By the way, 2 regular economy seats is not going to give you extra legroom, you just wont have anyone next to you (if that is even allowed). A premium economy seat is located in areas that have several extra inches of legroom to the front of you, so if you've got longer legs it is more comfortable.

Is it because you're tall or because you're obese? You might just have to pay for premium if you want a wider seat.

Ask the airline.

If "leg room" is your only problem, and not your "hip room", I encourage you to ask for a seat by the emergency exit. Even if they're occupied on-line, you can usually ask at the check-in counter to have yourself re-located.

There are certain downsides such as having to stay calm and to help in case of an emergency evacuation, as well as not being able to put your luggage around your legs, but you can't ask for more "leg" room than that.

Otherwise, you should go for first class. It's worth the money as far as roomy in long distance is concerned.

Can I buy two economy seats and fly by myself?

Yes, there are common situations that call for a single person to purchase and occupy multiple seats. You'll have to contact the airline for their specific details.

I would like more legroom

Two seats can give you a bit more legroom as you can sit diagonally, though it will still be normally cramped during take off and landing when you have to face forward.

but and I can save over $200 if I was to buy 2 tickets instead of one

That is an odd pricing situation. Premium economy usually isn't that much more expensive, but maybe that's just how it is for your local.

See if the airline has 'extra leg room seats' that you can typically change to for a fee on the day of departure at the airport; I find those worth the upgrade, often better than paying a lot more for emergency row seats where you often get a lot of people standing in front of you on these long flights.

often better than paying a lot more for emergency row seats

Just to clarify, the emergency row seats cost just as same as the other seats of the same category (ie. if it's in economy class, you only pay the ordinary fee for economy).

Just to clarify, the emergency row seats cost just as same as the other seats of the same category (ie. if it's in economy class, you only pay the ordinary fee for economy).

That is not always true. There are airlines that charge an extra fee for rows with extra legroom such as the emergency exit rows.

Correct. Which is why I answered much earlier "to ask the airline."