Mark Krueger is a midfielder and the captain of Unicorn, the team representing the United States in the International Football Frontier tournament. In the alternate timeline of Inazuma Eleven Orion no Kokuin, he also serves as captain for Star Unicorn and later plays as a midfielder for Navy Invader. He has sandy blonde hair and teal eyes. His personality is calm, friendly, and approachable, with a strong sense of dedication and a cheerful disposition. He possesses an intense passion for his country and is deeply committed to representing America on the world stage. He is also known for being a serious and hardworking player, never giving up easily and investing himself fully in whatever he undertakes.

His role in the story is that of a formidable opponent and one of the world's best players. As captain, he leads Unicorn with tactical judgment and leads by example, earning respect from teammates and rivals alike. His key relationships include a close bond with fellow Unicorn player Dylan Keith, with whom he shares a friendly and cooperative dynamic. He also works alongside Kazuya Ichinose when executing their combined special technique. Notable abilities include his signature hissatsu techniques: The Icarus, which is a powerful solo shot; Unicorn Boost, a combined move with Dylan; and Gran Fenriri, a three-player technique performed with both Ichinose and Dylan. These moves showcase his skill, teamwork, and ability to coordinate with others effectively. His development throughout the series highlights his leadership and determination, consistently striving to elevate his team's performance and prove his country's strength in football.