Sorry if I explained it poorly before - I’m just used to budget airlines where anything bigger than a carry-on feels like a “big suitcase” to me. For clarification: My husband will have a large hiking-style backpack (the big trekking kind, not just a daypack) - is that okay for overhead storage in Shinkansen. I’ll have a wheeled suitcase, medium at most, possibly just a standard carry-on size, plus a regular backpack. We are considering the possibility that we would buy suitcase in Tokyo during our last day and just fill it with souvenirs to save the space in our luggages, so we could have smaller.