Is 11am still peak hour? Need reserve seat?

Do i need to reserve seats if i am intending to book shinkansen hikari train departing tokyo between 10.30am - 11.30am heading to Shin-osaka on 1 Dec 2019 (sunday)?

Also if travelling from Shin-osaka back to tokyo on 7 Dec (saturday) about the same time?

At the above time period, would the train be very crowded to get a seat if i did not reserve? Thank you.

Probably one of the busiest times for shinkansen travel. As tourists like to travel at these times.

I am a Japanese living in Tokyo and often go back to Gifu with Shinkansen via Nagoya.

It depends on the type of Shinkansen.
If you are JR pass holder and take Kodama, it you don't have to book, I think.
But weekday, I really recommend to book.

Do you need to? No.

Should you? For a fairly small premium (or free if you are on the Japan Rail Pass), then to remove the potential for standing part of the trip, then yes, you probably should.

If you were travelling solo, it is less of an issue, queuing early and finding a single empty seat is not too hard. If you were a bigger group, then maybe you like to sit together, and reservations allow that more often.

Thank you for all your helpful replies. I didn't know at 11am, shikansen would be the busiest with tourists travelling at this time. Thanks. And yes, i think i should probably reserve my seats since i am travelling with luggages and my family although my 2 children are already teens. Also, heard from a friend who visited japan that without reserving the seats, even if one manages to get an empty seat on the train, there is no guarantee that the seat will not be reserved by someone at the next station. If it is reserved by someone at the next station, we have to give up the seat.

Thank you for all the advices and information.

Also, heard from a friend who visited japan that without reserving the seats, even if one manages to get an empty seat on the train, there is no guarantee that the seat will not be reserved by someone at the next station. If it is reserved by someone at the next station, we have to give up the seat.

DO NOT sit in a reserved car if you do not have a reservation for that. Your friend did something pretty terrible if they did that or even suggested that.

The non-reserved cars are simply free seating. On a non-reserved ticket, you don't get to go into a reserved car. Even if you have a reserved ticket and choose to sit in a different seat, that is also considered very rude - I've seen it happen for tourists and Japanese people (who should know better), and the most recent case the passenger needed to get help from the conductor to sort out the person that was in their seat.

My short answer is, yes, you should reserve seats, because you're a family of four. There is no reason not to. Ask for seats A, B, C, D and E, so that you could all sit next to each other in 1 row.

My longer answer is this: It is possible, and commonly done, to queue for your next or next next train to sit at the non-reserved sections. All trains bound for Osaka depart from Tokyo, so as long as you are around the top of the queue, you can get seats. If you were a solo traveler in early December, I may have recommended you to queue instead of reserving.

Another option is to ask the conductor after you board the train. The conductor would know if there are unoccupied seats in the reserved section, and if there is, you may sit there (by paying the reserved seat fare if you only have a non-reserved ticket). In peak dates such as Year-End, the trains would be so crowded that you cannot reach the conductor, but in early December, you can easily visit the conductor's room or ask when (s)he comes around to check your ticket.

As a local Japanese traveler, I've come to realize that one disadvantage of reserving a seat is that you sometimes end up stuck in an unfavorable seat, moreover next to an unfavorable passenger, which may happen in any type of transportation around the world especially if you're a young solo female. But since you're a family, you can have the whole row of 5 seats to yourselves, including ocean side and Mt. Fuji side. Plus, by reserving seats you can avoid the fuss trying to sit close together.

If you happen to miss your reserved train, you can still board the non-reserved section of any other train of the same route and type.

Enjoy your trip!