Ticket reservations in Tohoku shinkansen

Hi All,
I am traveling to Tohoku this autumn and will be using the JR East Tohoku pass. I will be using the pass to travel in below routes:
1. Tokyo to Kakunodate
2. Kakunodate to Towada (via Hachinohe)
3. Towada to Sendai
4. Sendai to Aizu Wakamatsu
5. Aizu Wakamatsu to Tokyo

In the JR East website, it is mentioned like - "Reservations can be made from one month before your travel date up until 11:40 p.m. (23:40, Japan Standard Time) 3 days prior to your travel date".

My doubt is, can I reserve a seat on the day of travel directly at the train station or is it safe to plan in advance which train I am going to take on a particular day, and reserve the same few days prior to my travel date (for a guaranteed seat)? I have travelled in Tokaido shinkansen in previous trip, and didn't feel the need to reserve tickets several days in advance because of the high frequency of trains in that line. Now I wanted to clarify if the same would work with Tohoku shinkansen as well.

Your suggestions will be very helpful. Thanks in advance for the same!

The earlier you reserve a seat. The more likely a perticular service wont be full.

If you wanna wait until the day of travel. Then just be prepared to be flexible with which train to take.

I personally wouldnt rick it considering some of you distinations have limited local trains you need to transfer to.

I personally wouldnt rick it considering some of you distinations have limited local trains you need to transfer to.

That is wrong. The only destination that is served by local trains is Aizu-Wakamatsu, and local trains from Koriyama are quite frequent (not to mention that Shinkansen to and from Koriyama have non-reserved seats as well).

You could reserve the seats and then still change your mind later. There isn�ft any penalty for it.

Thank you everyone for your suggestions!

From what I understand, it is better to reserve in advance for the shinkansen tickets.

up until 11:40 p.m. (23:40, Japan Standard Time) 3 days prior to your travel date
That refers to on-line reservations.
At a ticket office you can reserve a seat from 10 am a month prior to basically 1 minute prior. So when you get your pass, you could do all your seat reservations and tickets at that stage.

If you are not particular which train you take ( meaning time, date) then you can turn up when ever.

On one occasion recently, knowing how frequent trains are between Sendai- Tokyo, I left it till the day before to reserve my ticket. It was a bad decision. Turns out that period was super busy - people were going for job interviews, end of school etc etc - I learnt my lesson!

Anyway reservations online is easy, you can change either online or at the station if your plans change at no cost.

Sorry for the late reply!

@JapanCustomTours.
That refers to on-line reservations.
--> Thank you! I was exactly looking for this information.

At a ticket office you can reserve a seat from 10 am a month prior to basically 1 minute prior. So when you get your pass, you could do all your seat reservations and tickets at that stage.
--> Ok. I will try to reserve in advance when I know my exact time of travel for a particular place.

@grobea.
On one occasion recently, knowing how frequent trains are between Sendai- Tokyo, I left it till the day before to reserve my ticket. It was a bad decision. Turns out that period was super busy - people were going for job interviews, end of school etc etc - I learnt my lesson!
--> Thanks for letting me know of this! I will try to reserve too from Sendai to Tokyo too (and wherever I know the exact date and time)
If you are not particular which train you take ( meaning time, date) then you can turn up when ever.
--> Thank you!