A declaration from the emperor could frame renewed cooperation with Britain as an alliance between monarchies. That would give Yonai a way to challenge pro-German opinion without presenting the choice solely as an argument over foreign policy. Germany no longer had a Kaiser, while Britain's king could be described as a fellow sovereign deserving imperial support. Yonai's recognised closeness to the emperor would also raise the political cost of attacking him. This proposed protection depends on imperial endorsement and the particular standing Yonai enjoyed at court.
Notable Point · 1:13:17-1:16:38
Imperial endorsement could weaken Japan's pro-German faction
Yonai could present support for Britain as loyalty to a fellow monarch, making resistance to the alliance harder for Japanese nationalists.