Also, Japan requested that China recall this ambassador because after Takaichi's comments, he was the first to respond by calling for chopping off Japan's filthy head if it sticks its neck out over Taiwan. We refused. He's there now to show Chinese defiance, not as a symbol of friendship or cooperation anymore.
I wanna go back to this point because it was nothing but a passing thought before but Bent Back Kanae came to China offering for Takaichi to probably offer some public half-measure, although directly targeted, at climbing down from her statements on a Taiwan conflict (she probably cannot do a full apology as that would be political suicide) if China would recall Xue Jian for his comments. They tried to imply that China should save face by recalling him or Japan will expel him. China's refusal challenged Japan to expel him if they dared, but Japan folded and with that, it means that
Japan must live with the insult of continuing to host a foreign diplomat who threatened to cut the head off of his host. Most painful indeed; if any diplomat were to make such a threat against China in China, we would probably have him expelled, deported, sanctioned and removed so fast he'd need someone else to send his things to him back home.
And upon closer look, Xue Jian is not the ambassador to Japan but I guess with Japan folding on him, China did not increase the pressure by recalling Chinese or expelling Japanese diplomats. That would be kept in reserve should Xue Jian face issues in Japan.