This species most likely belong to the animal kingdom, because it is multicellular with no cell wall.
Members of the kingdom Animalia are eukaryotes (organisms with true nucleus), multicellular and their cells do not have cell wall. If the cell had a cell wall, the specie could be a plant or fungi, but it does not have a cell wall so it is an animal. Animals exist in various sizes and colors and their cells contain many organelles that perform several functions that are important for their survival.