If sushi must stay overnight, it needs to be refrigerated. Keeping it in the refrigerator is an option. The temperature should not be too cold in case the sushi rice is too hard. If you put it on sale for a long time, you can spread ice cubes under it, which is generally the practice in the canteen. Sushi sold in Korean food supermarkets is sold in freezers and can be placed overnight. However, it is usually sold at a reduced price the next night to avoid overnight storage. If you are holding sushi, you can spread lemon juice or miso on the fillets and add sushi vinegar to keep them fresh and delicious. (Lemon slices are put directly on it, which tastes delicious-mirin, a Japanese cuisine seasoning) Banana sushi is usually ready to eat. Take making sushi rolls as an example. If you put it inside, you can fry it with TAMPURA powder or wrap it with bread flour. Can solve the problem of oxidation blackening. If the slices are spread on the roll, you can soak the banana slices in glutinous rice first, or pour the yuzu juice on the banana roll. Another suggestion, if your sushi needs to be kept for a long time. Mango and pineapple replace bananas as fruit ingredients. These two can be preserved for a long time without special treatment. I'd like to add a suggestion. Sushi that stays overnight can be processed separately. Holding sushi, you can sprinkle seven flavors on the noodles, and then burn the fish noodles with a flamethrower until they are slightly burnt, which becomes another delicious food. This is also one of the ways to hold sushi. For sushi rolls, put them flat, spread them with spicy mayonnaise, or mix them with chopped ingredients such as fake crab sticks, spread them on the rolls, and bake them in a small oven until the spicy mayonnaise is slightly burnt, either hot or cold. In this way, a sushi will become another sushi with a little processing.