Normally reserved seat in advance are only for those travel during Golden Week or wanted to ride those super rare sightseeing train.
Reserved seat in advance are advance tight your schedule in that particle timing which is very stupid specially Tokaido Shinkansen got 90 train schedule running from Tokyo to Fukuoka vice versa daily. As long no holiday, 100% confirm got seat & train not even 50% full.

If you reserved seat in advance:
From lake Kawaguchiko to Mishima Station bus got any delay. You are fxxx, late 5 minute you are fxxx because Shinkansen are super duper on time. Example 10:30 am train, 10:20am train will be arrived platform & 10:30am sharp door will closed. Japan buses sure will delay because road condition always unpredictable. Seat reservation will making you need to arrived Mishima Station 30-40 minute in advance.  So stupid.......you making your journey from Kawaguchiko to Mishima like Amazing Race for something had 90 schedule train running daily which is every 15 minute will had one train from Tokyo heading Kyoto.

Oh yea, you reserved in advance, you late, you will burn that 16,000 Yen - 20,000 yen Ticket.

I see, thanks for the insight. I  will be travelling late March to Early April. Is this consider peak period? 

So, in this case, I can still reach the Mishima station first, buy the ticket, reserve the seat for the train coming in 30 minutes and  take my sweet time to walk to the platform?

Thanks again. Else I am farked....😅😅😅

Seat reservation can be done even if the train arriving in 5 mins if they still have seats available (which usually have). If not, just reserve the next train and relax at the station by strolling around or browse FB

Good idea!! Thank you!!

So, means the trains has a No# right? Else how I know the ticket is for which correct train?

Example:
It will be Kodama こだま No.25 & Next train will be Kodama こだま No.32.  Normally Kodama こだま are higher frequency to Nagoya Station. From Nagoya Station you can take another Hikari / Nozomi Class to Kyoto Station. 

From Mishima got Kodama Train to Kyoto Station, frequency is about every 1 hour per train compare frequency to Nagoya Station (25 minute per train)
* Mishima Station are not Major Station,  Shinkansen Nozomi & Hikari Class does not stop at Mishima Station.

I see. This means I wait for Kodama 25 right? Ermm..how do I know if the train has passed (for whatever reason), so I dont wait around like an idiot...

So means Mishima I can only take Kodama every hour. I am actually trying to decide whether I should pusing balik using Train to Shinjuku to take the Shinkansen or take bus to Mishima....what is your opinion?

When you reach the station,  buy the ticket from JR Ticket Office. Once you got the ticket (normally will be the next arrived train). From ticket you got the train no. Info. Seat no. And coach no.

Train no. Info can get from big info monitor similar to airport. Big info monitor will show next train arrived time and which platform.

Example of Shinkansen Ticket.

Nagano & Takayama should be switch around for making the trip more flow smoothly. I go better plan.

April Takayama hotel price will be sky rocket because of reopen of Tateyama Alpine Route. 5 night at Tateyama are too overkill unless you want go deep sweet travel style.  Takayama can reduce to 3 days 2 night will be far enough.

Tokyo - 5 nights
Tokyo > Nagoya > Takayama with JR Limited Express "Hida".
Takayama - 2 night (Shirakawago and Kamikochi with Nohi Bus)

Takayama > Toyama with JR Limited Express "Hida" and stay at Toyama 1 night
Toyama > Tateyama Alpine Route with "Toyama Dentetsu" until Tateyama Station.  Tateyama Alpine Route another side of ending will be JR Shinano Omachi Station. From Shinano Omachi Station take JR Local train to Matsumoto Station. Enjoy the beautiful Oito Line scenic View.
Matsumoto Station can continue to Nagano Station with JR Limited Express "Shinano".

Nagano - 2 nights

From Nagano > Kanazawa with Hokuriku Shinkansen and stay 1 night at Kanazawa.
Kanazawa > Shin-Osaka Station with JR Limited Express "Thunderbird"

Osaka - 5 nights - 2 days trips to Kyoto
Tokyo - 3 nights - kawaguchi and Disneyland

Thanks for the details,  very informative! But a bit too packed as we are travelling with a kid.

Love your idea on Tateyama, I’ll see how I can take one day off Takayama to make way for this, either before or after Takayama.

I’ll need to go Nagano first as that will be one of the last places with cherry blossom, plus the whole Alpine route, I found from google map that ogizawa is permanently closed? So I might just do a half trip up until the snow wall and come back down again.

Once April, Ogizawa will reopen.

And for laundry, I found some info on coin laundry but not much, might be handy to have some tips as I think I’ll need it since travelling with kid

I find that many hotels in Japan offers self laundry room complete with detergent and softener dispersing machine.

Ah ok, I saw a few places which are temporarily closed like Kamikochi but it’s the first time is see permanently closed.

While reshuffling my schedule, are you able to share your experience on luggage and laundry? The usual hotel check in time is 3pm and check out is 10-11am, do you just leave the luggage with the hotel concierge or do you use those lockers at the train stations?

I find that many hotels in Japan offers self laundry room complete with detergent and softener dispersing machine.

kenji1903 is golongan T1 won’t stay the business hotels that have coin laundry one rah.

How are you bro?

Haha ok ba. Planning Sakura trip and also trying to figure out if I can do laundry or if I need to pack an entire 2 weeks worth of clothes. And if I can/should fit in winterwear for a gala yuzawa daytrip for the kiddo to experience snow.

Wah bro, play snow need a lot of gear wor, water proof pants la, snow boots la
I will most probably pack 2 weeks, it’s troublesome to have so much luggage hopping from city to city but no choice la, coin laundry also need to wait 1 hour for wash and dry…