otsu was born in mito on march 24, 1990. after graduating from seiritsu gakuen high school, he joined j1 league club kashiwa reysol in 2008. he played many matches from first season. however kashiwa was relegated to j2 league end of the 2009 season. in 2010, kashiwa won the champions and was returned to j1 in a year. in july 2011, he moved to german bundesliga club borussia mönchengladbach. however there were few opportunities to play. in 2012, he moved to dutch eredivisie club vvv-venlo. although he played many matches, the club was relegated to eerste divisie end of the 2012/13 season. in january 2015, he returned to his first club kashiwa reysol. in 2018, he moved to yokohama f. marinos. yokohama won the j1 league champions in 2019. in 2021, he moved to j2 club júbilo iwata.