Sell car to a friend. Is it complicated?

I'd like to sell my car to my friend on leaving Japan. What is required in terms of paperwork and is it easy to get through?

it is easy to sell a car. but, registration is not so easy.
since the car owner is the second responsible person about the car, you should confirm that all the official registration paper works have been done, before you leave.
I advise that you ask the paper works to a car dealer. it is not cheap. but, you don't need to worry about the trouble. generally speaking, the fee should be paid by the new owner.

You can find important words.
http://www.japan-guide.com/forum/quereadisplay.html?0+136877

What is the difference to whom to sell? But it is necessary to deal with the documents. Maybe just let the proxy goes?

Guys, thanks, but from 3 replies I didn't understand a word you've said. Online translation does NOT work......

Oh, Ken.
Sorry, not included in my previous remark, but your answer also just tells me basically, yeah, I need docs, and, um, I know that, but it doesn't tell me what I asked: WHAT docs and what IS the process.

car registration.
http://car.naru2-shop.com/

I assume that the officers at 陸運局 are probably not friendly to persons unfamiliar for the process. your application will not be accepted until you gather all documents correctly.
again, car registration should be done by the new owner.

again, car registration should be done by the new owner.
A bit NOT correct about "by the new owner" part.
Not only by new owner "By 行政書士" also possible but need 委任状 plus.
(If bought at car shop, by car shop staff instead customer usual)

行政書士(ぎょうせいしょし/gyou-sei-sho-shi)??
Certified Administrative Procedures Legal Specialist
(limited laws specialist just not unlimited lows specialist "lawer")
(also 司法書士/しほうしょし/shi-hou-sho-shi possible but not usual)
Their office/事務所(じむしょ/ji-mu-syo) placed
near 陸運局(りくうんきょく/riku-unn-kyoku/registration office) usual.
陸運局 also called 陸運支局(riku-unn-shi-kyoku means brach)
or 陸事(riku-ji) means short of 陸運支局事務所(riku-unn-shi-kyoku ji-mu-syo)
But for 軽自動車(Kei car/Yellow plate small engine one) registation cannot at 陸運支局
also some offices location placed different address but not so far from 陸運支局.
BC K car's office belonging 軽自動車検査協会(Kei-ji-dou-sha ken-sa kyou-kai).
(Light Motor Vehicle Inspection Organization)
陸運支局 is for "White plate" car's mainly office.
(some offices location 軽自動車検査協会 with)

委任状(いにんじょう/i-nin-jou)?
Letter of attorney
http://knowhowrashinban.web.fc2.com/eigode.pdf
http://car.naru2-shop.com/inin.html

Anyway, recommend asking at city/town hall
about EN speaker's 行政書士事務所 place or TEL number first.
BC I know all well but would like to explain all process (above last link ステップ/step 1 to 7)
and can not be confirmed your car is llegal one or not. (most important point)
Also "Y number plate" car or not.

If llegal one,paper work need 5 days to a week(next week) fr police station paper work.
http://www2.kek.jp/rso/Living/Buy_Change.html
Car registraion office work under 2 hr total.(lunch break exist)
Comfirming "Parking place certificate" by Police(not by Police man) need 3 to 5 days(result shows next week).
I didn't check content below(not official documents) all but seems mostly right way.
https://okijets.wordpress.com/lifestyle/cars/
(kanji "車庫署名賞" is typo "車庫証明証" is)

Or, someone may knows or gives big hints.
http://gaijinriders.com/ (famous mortorcyclist forum)
https://forum.gaijinpot.com/forum/living-in-japan/travel-transportatio...
(one of Old Q)
And some Exporters who also have own YouTube channe seemsl looks like friendly.
http://pacificcoastjdm.com/
https://www.micklay.com/
http://www.smilejv.com/

I just did a google search of "buying a car in Japan" and several websites popped up. Here's one website that lists the papers you need: http://www.supermelf.com/japan/ajetdrivingbook/chap1.html

When I bought a car from a friend, I don't remember it being a terribly difficult process to do myself (although it was a long time ago so I don't remember what paperwork I needed exactly). My only problem was that at first I didn't drive the actual car there, but it turns out I needed to get a new license plate, so I had to go back with the actual car a different day. Otherwise, the paperwork seemed straight forward.

When I sold that car, the other person had a lot of trouble. First, I hadn't updated my shakken form with my new address, so iI had to get proof that I used to live there but moved (I should have done this when I moved and just forgot). There was also something wrong with their information too, so in the end it was a big hassle for both of us and took a long time to correct. So as long as your information is correct across all the paperwork, the other person should have no trouble transferring the car. So just check beforehand.