Teletha Testarossa, commonly known as Tessa, is a central character in the anime series Full Metal Panic! She is the Captain of the submarine Tuatha de Danaan and a high-ranking officer of the Mithril organization. Despite her young age, she is a prodigious military strategist and leader, often displaying great courage and intelligence in high-pressure situations. Tessa is known for her kind-hearted nature, compassion towards her subordinates, and her complex relationship with protagonist Sousuke Sagara, as she harbors romantic feelings for him. Her character adds depth and intrigue to the series.