Most of Don Don Donki's products are indeed from Japan, but do take note that they are generally considered at the lower end of the price and quality spectrum in Japan, so you need to be realistic with your expectations as well.
The food items are worth it as they are only 30% - 50% more expensive than Malaysia/Thailand made ones but better quality. Sashimi/Sushi around same price and quality as NTUC or Cold Storage. I wouldn't bother with any of those other household items, they all cost easily at least 3x - 4x the normal Made in China ones and around the same quality.