If the Emperor of Japan were watching what happened to China with European imperialism in 1855:
1. His policy towards Europeans would be to adopt some of their modern ways, like technology and military, in order to strengthen Japan against potential imperialist threats.
2. He would want to avoid China's fate of being colonized by engaging in limited cooperation and trade with Europeans while maintaining Japanese independence and traditions.
3. The Emperor would likely continue to isolate Japan from unchecked European influence, as was the policy, but also begin preparing Japan's military to potentially fight off imperialist encroachment as needed.