Katsuya Okada
Nagatsuma continued to rise through the ranks of the party after the 2012 defeat. He became DPJ's deputy secretary-general in May 2013. After then-party leader Banri Kaieda was defeated in the 2014 election, Nagatsuma entered the race to succeed him, but lost to Katsuya Okada. Okada then appointed Nagatsuma to be the party's deputy leader, a position he held even after the merger with Japan Innovation Party.