In the picture below, the left four are Western style and the right 5 are Japanese style in the back row (This is the first batch that we grilled, we had much more). Aren't they cute? The front row is smashed and grilled potatoes. I think this definitely qualifies for Izakaya food.
Japanese style marinade: Sake, Mirin, and soy sauce (1:1:2) with several slices of fresh ginger.
I marinated the octopuses for several hours in the refrigerator. I drained the marinade and simply grilled them for 2-3 minutes turning frequently (below, left). As per my wife's idea (she got the idea from one of the issues of Cook Illustrated), she microwaved baby red potatoes, then coated them with oil and smash them flat. We then grilled both sides (below, right).
Both styles had lots of flavor, especially the Western version had nice lemony and thyme flavors. Only problem was that both were a bit chewy. For most Japanese, this degree of chewiness is Ok but not for most Westerners including my wife. I ended up cutting them into small pieces.
Our neighbor's dog showed up and hung around despite her owner's calling. She was not about to leave our barbecue. She may get in trouble if this continues.