Combine all the ingredients except the oil. Then add the oil in a stream and season.
Mix the sugar with the sodium alginate and whisk in the truffle juice using a hand mixer. Prepare a calcium bath by combining the calcium chloride with the water. Inject the truffle juice mixture into the calcium bath with a syringe. Wait two minutes, then pour the calcium bath and caviar through a very fine mesh strainer and rinse the caviar in cold water.
Dip one 5 x 2.5 inch tuna sashimi in the white soy sauce and spread the coconut sauce on it. Arrange the rest of the ingredients on top of the coconut sauce. Place a small spoonful of yuzu koshu paste on the plate and cover it with the honshemeji mushrooms rolled in lomo.