In May 2020 I'm riding my bike from Tokyo to Sapporo!
Sounds like a great plan. I cycled 1,5 years ago from Wakkanai to Kyushu (but also took A LOT of other modes of transport ) and really enjoyed it. I kept a blog with my experience but also with some general practical tips. If you want to check it out itfs here: http://bicycletraveljapan.blogspot.com/
(Note that I am no strong cyclist so no hills.)
If you can make it through Oma to Hakodate I would strongly advise to get up to Osorezan and have a soak in one of their acidic onsen. Are there bike friendly hostels in Shinjuku (or in whole Tokyo) where I can take my bike inside (my room) and store my bike box for one month(which I need to take my bike on the airplane)?
Sorry I donft know about hostels or accommodation in Tokyo as I used to live there. And now when I go fror business I go to relatively cheap business hotels. They DO allow bicycles in the room though. Mine is however a very small brompton so I can still move in the room. I normally however try to park outside.
However you could just park your bicycle outside on the street. Just need a normal lock. Some areas in Tokyo are no parking areas which means there are designated parking lots. You pay for them a bit. Other areas you can park your bicycle as you want. Donft rough park because there is police going to tow your bicycle.
Regarding the box , a month is a long time. There is some long term baggage storage at Tokyo station, but that could cost quite some. You could also contact a hotel or hostel and just ask them. If you stay again for a few nights before leaving they might agree to it, but itfs asking quite something as space in Tokyo is so limited. You could ask a bicycle tour shop in Sasazuka ( look it up, but they are also on Airbnb) if they would be willing to keep your box for a months. tHey are a friendly bunch of people and quite into cycling so maybe. Any recommandations for bikeshops in this area?
Y roads in Shinjuku close to Shinjuku San chome. They are in a basement and have repair and sell racing bicycles among others. Next question, I'll be taking the train from Shinjuku to Takaosanguchi Station, where I'll start to cycle. Any advice at what time it is less crowded so I can easly take my bike on the train?
Not sure if you are aware, but no gnudeh bicycle is allowed on any trains / bus in Japan ( well technically speaking there are 2 or 3 train lines that allow it, but in a country with thousands of train lines itfs practically none. And definitely the train from Shinjuku to Takaosanguchi isnft one of them). Thus you MUST bring a bicycle bag. Once your bicycle is in that bag you can bring it on any train you like. It has become luggage in the eyes of the train company. You might consider if you can fly directly with just a cycling bag instead of the box. Or maybe use a card board box and get a new one before leaving. (I was traveling with a brompton and whenever I needed to bring it from Europe to Japan I just got a new box from a local brompton store and used it for that flight only. For flights inside japan I checked in the gnudeh bicycle. Now my faithful brompton is stored below my desk at my Tokyo office waiting for me to come back in autumn. )
Regarding crowdedness of that train. I think there are 3 things to consider:
1) crowdedness of Shinjuku Station
2) crowdedness of the train itself
3) need to have the bicycle in the bag from the moment you pass the turnstiles.
1) worst in the morning rush hour, but essentially never gets really empty. Possible work around: visit on foot first and find the nearest entry for the KEIO line you are going to take. Or cycle to the next stop and take train from there. There are express and non express trains, so there are more or less convenient places. But eg cycling to Sasazuka from Shinjuku is only about 20 min and you can cycle most of the way on a nice neighborhood small road. Which starts here :
Near 4-chōme-28 Yoyogi, Shibuya City, Tōkyō-to 151-0053, Japanhttps://goo.gl/maps/Ew15QX1BFk6eHaDj9
2) On weekdays in the morning you are going anticyclical so it should be no problem at all. Just avoid the evening rush hour. But if you want to start cycling in Takaosanguchi then youfll start in the morning anyway.
3) which means the less path there is between the turnstiles and the platform the better. Thus my recommendation for smaller station.
Enjoy your ride!