In 2011, he started working as lawyer specialising in cases of medical malpractice. He recontested the Niigata-5th seat in the 2012 election as a member of the Japan Restoration Party (JRP), this time finishing third. In the 2013 House of Councillors election, the JRP fielded him as their candidate for the Niigata at-large district, finishing fourth behind the three incumbent Councillors. Yoneyama would follow the party in its two subsequent mergers, first into the Japan Innovation Party and later into the Democratic Party.