My friends and I got some food while in Japan. I've been trying to figure out what the sauce is that was used on the burgers in the pics.
Not sure if this helps, but the instructions for the burgers on rice was to brown one side, flip the burger, cook for 1-2 mins, add sauce, reduce heat and simmer for 8-10 minutes. The packet was refrigerated and stored next to the burgers in the grocery store.
I've tried 2 different brands of Tonkatsu sauce and tried to make my own. The 2 brands were both too salty and the homemade version just wasn't it.
by Ingemi219