Kumagai was born in Sapporo on October 17, 1990. After graduating from Tokiwagi Gakuen High School, she joined for Urawa Reds in 2009. The club won Nadeshiko League championship in 2009 season. In July 2011, she moved to German Bundesliga club Frankfurt. After she played 2 season, she moved to French Division 1 Feminine club Olympique Lyonnais in June 2013. Kumagai scored the decisive penalty for Lyon in the 2016 UEFA Champions League Final, following a player-of-the-match performance.